Nickel-based superalloys : A guide to the selection and application of nickel-based alloys

An alloy composed of nickel as the base and other elements is called a nickel-based alloy. Nickel has excellent mechanical, physical, and chemical properties. Adding appropriate elements can improve its oxidation resistance, corrosion resistance, and high-temperature strength and improve certain physical properties. Nickel alloys can be used for electronic tubes, precision alloys (magnetic alloys, precision resistance alloys, electric heating alloys, etc.), nickel-based high temperature alloys, nickel-based corrosion-resistant alloys, and shape memory alloys. Nickel alloys are widely used in energy development, chemical engineering, electronics, navigation, aviation, and aerospace sectors.

Nickel can form various alloys with copper, iron, manganese, chromium, silicon, and magnesium. Among them, nickel copper is the famous monel alloy, which has high strength, good plasticity, and stable chemical properties in atmospheres below 750 degrees. It is widely used in the electrical industry, vacuum tubes, chemical industry, medical equipment, and marine industry.

What are nickel-based alloys?

Nickel based alloys are generally called alloys with a Ni content exceeding 30wt%. Common products have a Ni content exceeding 50wt%. Due to their superior high-temperature mechanical strength and corrosion resistance, nickel-based alloys, together with iron based and cobalt based alloys, are called superalloys. They are generally used in high-temperature environments above 540 ℃, and different alloy designs are selected according to their usage scenarios, often used in special corrosion resistant and high-temperature corrosion environments. Equipment with high-temperature mechanical strength is required. It is often used in aerospace, energy, petrochemical industry, or special electronics/optoelectronics.

The role of elements in nickel-based alloys

When it comes to nickel-based alloys, we must first talk about the nickel element.
Like iron and copper, nickel has been used as an alloy since it entered civilized society. But nickel alloy was a latecomer to the chemical industry compared to steel, brass, and bronze. With the continuous progress of metallurgical and manufacturing technologies, the development of nickel alloys has been promoted, promoting their widespread application in the chemical industry. Nickel alloy combines excellent corrosion resistance, strength, toughness, metallurgical stability, processability, and weldability. Many nickel alloys also have excellent heat resistance, making them an ideal choice for applications that require high temperature strength and chemical corrosion resistance at high temperatures.
The main function of nickel in nickel-based alloys is that it changes the material’s crystal structure. One important value of nickel in nickel-based alloys is the formation of austenitic crystal structures, thereby improving factors such as plasticity, weldability, and toughness.
The roles of various elements in nickel-based alloys, except for nickel, are as follows:

• The effect of boron and silicon elements: significantly reduce the melting point of the alloy, expand the solid-liquid temperature range, and form low melting eutectic; Deoxidization reduction and slagging function; The hardening and strengthening effect on the coating; Improve operational process performance.
• The role of copper element: improving corrosion resistance to nonoxidizing acids.
• The role of chromium element: solid solution strengthening effect, passivation effect; Improve corrosion resistance and high-temperature oxidation resistance; The excess chromium easily forms hard phases of chromium carbide and chromium borohydride with carbon and boron, thereby improving the hardness and wear resistance of the alloy.
• The role of molybdenum element: With a large atomic radius, the lattice undergoes significant distortion after solid solution, significantly strengthening the alloy matrix, improving the high-temperature strength and red hardness of the matrix; It can cut off and reducing the network structure in the coating; Improve the resistance to cavitation and erosion of nickel-based precision alloys.

Characteristics of nickel-based alloys

Especially ordinary nickel chromium alloys are characterized by their extremely high heat resistance of up to about 750 degrees Celsius, thus being able to withstand constant loads close to the melting point. They also have excellent scalability and tensile strength, low thermal conductivity, good cold forming performance, and high corrosion resistance. Low density, high chemical resistance, and high wear resistance make this alloy particularly suitable for high-temperature applications where aluminum and steel are unstable.

The favorable application characteristics of alloys make machining more difficult: relatively low cutting speeds can only be used in areas with short tool life. The standard tool life is a few days when using uncoated hard alloy cutting tools to process aluminum. For the processing of ductile iron, the tool life decreases to about one hour, while for nickel-based alloys, the life is between five to ten minutes.

• Nickel alloy is more expensive than stainless steel. However, an economic comparison based on the initial cost rather than the life cycle cost may need to be more accurate. For example, the price of Ni-Cr-Mo alloy is about 5 times that of 18Cr-8Ni stainless steel and 2 times that of super austenitic stainless steel. However, due to the excellent corrosion resistance of nickel alloys, the initial cost can often be compensated by the extension of equipment life, the reduction of maintenance costs, and the long-term cost savings brought about by minimal downtime.
• The physical properties of nickel alloy are very similar to those of 300-series austenitic stainless steel. The thermal expansion rate of nickel-based alloy is roughly equal to that of carbon steel but significantly lower than that of 300-series stainless steel. 
• Although the thermal conductivity of pure nickel is higher than that of carbon steel, the thermal conductivity of most nickel alloys is significantly lower and in some cases, even lower than that of austenitic stainless steel.
• In addition to pure nickel, the strength of nickel alloy used in the chemical processing industry is much higher than that of 300-series stainless steel. The nickel alloy also has very good ductility and toughness. The maximum allowable stress of most alloys used in chemical equipment is shown in ASME Boiler and Pressure Vessel Code Volume VIII.
• Nickel alloy is a full austenite microstructure. Almost all nickel alloys used in the chemical industry are solid solution strengthened. The improvement of their strength comes from the addition of effective hardening elements, such as molybdenum and tungsten, rather than the formation of carbides. Like austenitic stainless steel, solid solution nickel alloy cannot be strengthened by heat treatment but can only be strengthened by cold working.
• Another large class of nickel-based alloys can be strengthened by precipitation-hardening heat treatment. Most of these alloys are specifically used for ultra-high strength applications, such as alloys used in deep oil and gas production and ultra high pressure processes.
• Precipitation hardening nickel-based alloys have limited application in chemical equipment except for valves and rotating machinery components. These alloys include gas turbines, combustion chambers and aircraft.

Representative works of nickel alloy

The first commercially important nickel alloy was alloy 400, which was developed and marketed by the International Nickel Company (later known as Inco Alloy Company) in 1905 under the trademark MONEL.
The next important milestone was the introduction of nickel molybdenum alloy B and nickel chromium molybdenum tungsten alloy C around 1930. Their inventor is Haynes Stellite Company (now known as Haynes International), with two registered trademarks being HASTELLOY.
The next important stage in the development of nickel-based alloys came from Inco Corporation, which developed nickel chromium iron alloy 600 in 1931 and nickel iron chromium alloy in 1949, named INCONEL and INCOLOY, respectively. Inco and Haynes have utilized these trademarks’ initial recognition and reputation to launch approximately 50 corrosion-resistant and heat-resistant alloys in the MONEL, INCONEL, INCOLOY, and HASTELLOY series. VDM Company was a later well-known developer and producer of nickel-based alloys, with the trademarks Nicrofer, Nimofer, and Nicorros.

Development history of nickel-based alloys

Nickel based high-temperature alloys (from now on referred to as nickel-based alloys) were developed in the late 1930s. The UK first produced nickel-based alloy Nimonic 75 (Ni-20Cr-0.4Ti) in 1941. In order to improve creep strength and add aluminum, Nimonic 80 (Ni-20Cr-2.5Ti-1.3Al) was developed. The United States developed nickel-based alloys in the mid-1940s, the Soviet Union in the late 1940s, and China in the mid-1950s.
The development of nickel-based alloys includes two aspects: improvement of alloy composition and innovation of production processes. In the early 1950s, the development of vacuum melting technology created conditions for refining nickel-based alloys containing high aluminum and titanium. The initial nickel-based alloys were mostly deformed alloys. In the late 1950s, alloys were required to have higher high-temperature strength due to the increase in the working temperature of turbine blades. However, as the strength of the alloy increased, it was difficult or even impossible to deform. Therefore, investment casting technology was adopted to develop a series of casting alloys with good high-temperature strength. In the mid-1960s, directional crystallization and single crystal high-temperature alloys with better performance and powder metallurgy high-temperature alloys were developed. In order to meet the needs of ships and industrial gas turbines, a batch of high chromium nickel-based alloys with good thermal corrosion resistance and stable microstructure have been developed since the 1960s. During a period of approximately 40 years from the early 1940s to the late 1970s, the working temperature of nickel-based alloys increased from 700 ℃ to 1100 ℃, with an average annual increase of about 10 ℃.

Composition and properties of nickel-based high-temperature alloys

Nickel based high-temperature alloys are most widely used. The main reason is that, firstly, nickel-based alloys can dissolve more alloy elements and maintain good structural stability. The second is the formation of A3B type intermetallic compounds with coherent ordering γ [Ni3 (Al, Ti)] phase serves as a strengthening phase, effectively strengthening the alloy and achieving higher high-temperature strength than iron based and cobalt based high-temperature alloys; Thirdly, nickel-based alloys containing chromium have better oxidation resistance and gas corrosion resistance than iron based high-temperature alloys.
Nickel based alloys contain more than ten elements, of which Cr mainly plays a role in oxidation and corrosion resistance, while other elements mainly play a strengthening role. According to their strengthening modes, they can be divided into: solid solution strengthening elements, such as tungsten, molybdenum, cobalt, chromium, and vanadium; Precipitation strengthening elements, such as aluminum, titanium, niobium, and tantalum; Grain boundary strengthening elements, such as boron, zirconium, magnesium, and rare earth elements.

Nickel based high-temperature alloys have two types of strengthening methods: solid solution strengthening alloys and precipitation strengthening alloys.

Common Nickel Alloy Trade Names

Table 1 below shows some of the more common trade names of nickel alloy types sold on the market.

Table.1 Common Nickel Alloy Types and Trade Names

Name	Alloy type	Alternative trade names
Nickel 200	99% + pure Nickel	Nickel 99.2
Nickel 201	99% + pure Nickel	Nickel 201, LC Nickel 99.2
Monel 400®	Nickel-Copper	Nickelvac® 400, Nicorros® 400
Monel R405®	Nickel-Copper
Monel K500®	Nickel-Copper
Inconel 600®	Nickel-Chromium-Iron	Nickelvac® 600, Ferrochronin® 600
Inconel 601®	Nickel-Chromium-Iron	Pyromet® 601, Nicrofer® 601
Inconel 617®	Nickel-Chromium-Cobalt	Nicrofer® 617
Inconel 625®	Nickel-Chromium-Iron	Chornin® 625, Altemp® 625, Nickelvac® 625, Haynes® 625 Nicrofer® 6020
Inconel 718®	Nickel-Chromium-Iron	Nicrofer® 5219, Alvac® 718, Haynes® 718, Altemp® 718
Inconel X750®	Nickel-Chromium-Iron	Haynes X750®, Pyromet® X750, Nickelvac®X750, Nicorros® 7016
Incoloy 800®	Nickel-Chromium-Iron	Ferrochronin® 800, Nickelvac® 800, Nicrofer® 3220
Incoloy 825®	Nickel-Chromium-Iron	Nickelvac® 825, Nicrofer 4241®
Hastelloy C22®	Chromium-Molybdenum-Tungsten	Inconel® 22, Nicrofer® 5621
Hastelloy C276®	Nickel-Chromium-Molybdenum	Nickelvac® HC-276, Inconel® 276, Nicrofer® 5716
Hastelloy B2®	Nickel-Chromium-Molybdenum	Nimofer® 6928
Hastelloy X®	Nickel-Chromium-Iron-Molybdenum	Nickelvac® HX, Nicrofer® 4722, Altemp® HX, Inconel® HX
Vascomax® C250	Nickel-Cobalt-Molybdenum	Maraging C250™, Maraging 250™
Vascomax® 300	Nickel-Cobalt-Molybdenum	Maraging 300, Maraging C300®, and Vascomax® C300
Vascomax® C350	Nickel-Cobalt-Steel	Maraging C350™
Rene® 41	Nickel-Chromium
Multimet® N155	Nickel-Chromium-Cobalt
Waspaloy 25™	Nickel-Cobalt
Invar 36®	Nickel-Iron	Nilo 6®, Pernifer 6®
Invar 42®	Nickel-Iron	Nilo 42®

Trademark declaration:
The nickel alloy trade names, trademarks and registered trademarks mentioned in this article are the property of their respective owners, as follows:

• Hastelloy ® is a registered trademark of Haynes International, Kokomo, IN.
• Monel ®, Inconel ®, Ni Span ®, Nimonic ®, Incoloy ®, Nilo 6 ® and Nilo 42 ® are registered trademarks of Special Metals Corporation, New Hartford, NY.
• Waspaloy 25 TM is a trademark of United Technologies / Pratt & Whitney in East Hartford, Connecticut. 
• Pernifer 6 ®, Nimofer ® and Nicarros ® are registered trademarks of ThyssenKrupp VDM in Germany. 
• Nitronic ®, 15-7 MO, 15-5 PH, 17-4 PH, 17-7 PH, PH 13-8 MO is a registered trademark of AK Steel in West Chestertown, Ohio.
• Maraging C250 TM, Malagin 250 TM, Maraging 300, Maraging C300 ®, Maragiing C350 TM, Rene, Nickelvac ®, Nicrofer ® and Vascomax are registered trademarks of Allegheny Technologies ( ATI ), Pittsburgh, PA.
• Invar 36 ® is a registered trademark of Carpenter Technology Corporation in Philadelphia, Pennsylvania.
• Invar ® is a registered trademark of ArcelorMittal, Inc., located in.

Chemical composition of nickel alloys

The chemical composition of nickel alloys is the precise mixing of the elements that define their properties. Nickel, chromium, molybdenum, and iron are common alloying elements. These elements enhance corrosion resistance and strength and contribute to thermal stability.

Table.2 Chemical Composition of Common Nickel Alloys

Alloy	UNS (JIS)	Nominal Chemical Composition (wt%)						Heat Treatment	Tensile Strength (N/mm²)	Elongation (%)
		Ni	Cr	Mo	Co	Fe	others
Alloy 200	N02200 (NW2200)	≧99.0	–	–	–	≦0.4	C ≦ 0.15; Cu ≦ 0.2.	A	≧380	≧30
Alloy 201	N02201 (NW2201)	≧99.0	–	–	–	≦0.4	C ≦ 0.02; Cu ≦ 0.2.	A	≧340	≧30
Alloy 400	N04400 (NW4400)	≧63.0	–	–	–	≦2.5	Cu 28.0-34.0	A	≧480	≧35
Alloy K-500	N05500 (NW5500)	bal.	–	–	–	≦2.0	Cu 27.0-34.0; Al 2.2-3.2; Ti 0.35-0.85.	ST+AG	≧830	≧15
Alloy 600	N06600 (NCF600)	≧72.0	14.0-17	–	–	6.0-10	Cu ≦ 0.50	A	≧550	≧30
DSA 760	–	bal.	-38	–	–	–	(Al 3.8)	ST+AG	≧1,500	–
Alloy 625	N06625 (NCF625)	≧58.0	20.0-23	8.0-10	≦1.0	≦5.0	Al ≦ 0.40; Ti ≦ 0.40; Nb+Ta 3.15-4.15.	A	≧760	≧30
Alloy C-276	N10276 (NW0276)	bal.	14.5-16.5	15.0-17	≦2.5	4.0-7	W 3.0-4.5; V ≦0.35.	A	≧690	≧40
Alloy 22	N06022 (NW6022)	bal.	20.0-22.5	12.5-14.5	≦2.5	2.0-6	W 2.5-3.5; V ≦0.35.	A	≧690	≧45
Alloy CB3	N08020	32.0-38	19.0-21	2.0-3	–	bal.	Cu 3.0-4.0; Nb≦1.0.	ST	≧550	≧30
Alloy 25-6MO	N08925	24.0-26	19.0-21	6.0-7	–	bal.	Cu 0.5-1.5; N 0.15-0.25.	ST	≧650	≧35
DSP5	S35000	4.0-5	16.0-17	2.5-3.2	–	bal.	Mn 0.5-1.25	ST+AG	≧1,300	≧4

• A: Annealing;
• ST: Solution heat Treatment;
• AG: Aging

Mechanical properties of nickel alloy

Nickel alloys also have very good plasticity and toughness ( room temperature mechanical properties are listed in Table 3 ).

Table.3 The minimum value of mechanical properties of nickel alloy at room temperature

Alloy	Ultimate tensile strength ksi	Yield strength % ksi	Elongation%
200	55	15	40
400	70	28	35
600	80	35	30
625	110	55	30
690	85	35	30
825	85	35	30
G-3	90	35	45
G-30	85	35	30
C-276	100	41	40
C-22	100	45	45
C-2000	100	41	45
622	100	45	45
59	100	45	45
B-2	110	51	40
B-3	110	51	40
B-4	110	51	40

Classification of nickel-based alloys

Nickel-based alloy is a kind of alloy with high strength and certain oxidation and corrosion resistance at 650-1000 °C.
According to the main properties, it is divided into nickel-based heat-resistant alloy, nickel-based corrosion-resistant alloy, nickel-based wear-resistant alloy, nickel-based precision alloy, and nickel-based shape memory alloy. According to the different matrices, superalloys are divided into iron, nickel, and cobalt.

There are six main nickel alloy groups, namely pure nickel (for caustic service), nickel-copper and nickel-molybdenum (for reducing acids), nickel-iron-chromium (for oxidizing acids), nickel-chromium-silicon (for the so-called super-oxidizing acids, such as concentrated sulfuric), and nickel-chromium-molybdenum (the group which contains the most versatile alloys).

Reducing and oxidizing refer to the nature of the reaction at cathodic sites during corrosion. Reducing solutions like hydrochloric acid generally induce hydrogen evolution at cathodic sites.
Oxidizing solutions, such as nitric acid, induce cathodic reactions with higher potentials.

Nickel Alloys Main Groups & Uses

• Ni for Alkalis
• Ni-Cu for Reducing Acids
• Ni-Mo for Reducing Acids
• Ni-Fe-Cr for Oxidizing Acids
• Ni-Cr-Si for Super-Oxid. Acids
• Ni-Cr-Mo for Alkalis & All Acids

Nickel based corrosion-resistant alloy

The main alloying elements are copper, chromium, and molybdenum. It has good comprehensive performance and can withstand acid and stress corrosion. The earliest application (produced in the United States in 1905) was nickel copper (Ni Cu) alloy, also known as Monel alloy (Ni70Cu30). In addition, there are nickel-chromium (Ni Cr) alloys (which are nickel-based heat-resistant alloys and corrosion-resistant alloys), nickel molybdenum (Ni-Mo) alloys (mainly referring to Hastelloy B series), nickel-chromium-molybdenum (Ni-Cr-Mo) alloys (mainly referring to Hastelloy C series), and so on. At the same time, pure nickel is also a typical representative of nickel based corrosion-resistant alloys. These nickel based corrosion-resistant alloys are mainly used for manufacturing components for various corrosion-resistant environments such as petroleum, chemical, and power.

Nickel based corrosion-resistant alloy category

Nickel based corrosion-resistant alloys often have austenitic structures. Intermetallic phases and metal carbonitrides remain on the alloy’s austenitic matrix and grain boundaries in solid solution and aging treatment. Various corrosion-resistant alloys are classified according to their composition and characteristics as follows:
Pure nickel [2001 (UNS N02201)/200 (UNS N02200)]
It has excellent corrosion resistance to various reducing acids and salts but is unsuitable for strong oxidizing media such as nitric acid.
The most important characteristic of pure nickel is its unparalleled ability to withstand caustic soda, even molten caustic soda corrosion.
Although pure nickel exhibits outstanding corrosion resistance in dry halogen media, its corrosion resistance is insufficient below the water dew point.
For applications with temperatures not exceeding 600 ℉, alloy 201’s sibling brand – high carbon nickel 200 (UNS N02200) can also be used.

Ni-Cu alloy
Ni-Cu alloy has better corrosion resistance than nickel in reducing media and better corrosion resistance than copper in oxidizing media. It is the best material for high-temperature resistance to fluorine gas, hydrogen fluoride, and hydrofluoric acid without oxygen and oxidants (see Metal Corrosion).
Like nickel, nickel-copper alloy 400 exhibits the best corrosion resistance under reducing medium conditions, while gas and oxidizing chemicals are detrimental to its corrosion resistance. Alloy 400 is resistant to hydrogen halide and halide corrosion, especially to hydrofluoric acid and high-temperature gases containing fluorine or hydrogen fluoride. According to “Special Steel 100 Seconds”, it was developed in 1905. As an alloy with a history of 103 years, Monel 400 can be regarded as the “ancestor” of all nickel alloys. This alloy is widely used for treating sulfuric acid solutions, seawater, and saltwater. For applications requiring high strength, such as valve and pump components, alloy K-500 (NO5500) is often used, a precipitation hardening derivative of alloy 400.

Ni-Cr alloy
Ni-Cr, a nickel-based heat-resistant alloy, is Mainly used under oxidizing medium conditions. It is resistant to high-temperature oxidation and corrosion by gases such as sulfur and vanadium, and its corrosion resistance increases with chromium content. This type of alloy also has good resistance to hydroxide corrosion (such as NaOH and KOH) and stress corrosion.
Alloy 690 is the nickel-based alloy used in manufacturing pressure equipment with the highest chromium content and has strong corrosion resistance to oxidizing media. It can be effectively used in hot concentrated sulfuric acid, nitric acid, nitric acid/hydrofluoric acid mixtures, and oxidizing salt media. The high chromium content also improves the material’s corrosion resistance in high-temperature vulcanization environments.
Ni-Mo alloy
She is mainly used under corrosive conditions in reducing media. It is the best alloy to resist hydrochloric acid corrosion, but its corrosion resistance significantly decreases in the presence of oxygen and oxidants.
Alloy B-2 has outstanding corrosion resistance to reducing sulfuric acid, phosphoric acid, and hydrochloric acid. It is particularly suitable for hydrochloric acid equipment with a full concentration range and temperatures up to boiling points. Oxidizing chemicals hurt the corrosion resistance of this alloy, especially strong oxidants such as iron ions and copper ions that act as impurities in the solution. The later developed alloys B-3 and B-4 have better performance than alloy B-2, and one advantage of these new grades is that they minimize the formation of poor microstructures (which may cause embrittlement) during processing.
Ni-Cr-Fe alloy
Due to the alloy containing nearly 30% iron, alloy 825 is sometimes included in the super austenitic stainless steel series. It performs well in sulfuric acid and phosphoric acid media conditions, similar to Alloy 20, and its main development purpose is for use in sulfuric acid and phosphoric acid media. Although alloy 825 has acceptable resistance to hydrochloric acid corrosion, it is prone to chloride ion pitting and crevice corrosion, especially in non-flow and non-ventilated solutions. Alloy 825 has a high iron content, so its corrosion resistance to alkali and halogen is lower than that of alloys with higher nickel content.
Adding chromium to the nickel matrix expands the applicability of alloy 600 in oxidizing environments. Although alloy 600 has moderate corrosion resistance to inorganic acids, it has excellent corrosion resistance to organic acids, making it widely used in processing fatty acids. Alloy 600 is also widely used in producing, storing, and transporting hydroxides and alkaline chemicals. Alloy 600 is also an excellent material for high-temperature applications requiring heat and corrosion resistance. The excellent performance of this alloy in high-temperature halogen environments makes it an ideal material for organic chlorination reaction processes. Alloy 600 also exhibits excellent high-temperature degradation resistance, such as oxidation, carburization, and nitrogen.

Ni-Cr-Mo (W) alloy
Ni-Cr-Mo (W) alloy combines the properties of both Ni-Cr and Ni-Mo alloy mentioned above and is mainly used under conditions of oxidation-reduction mixed media. This type of alloy exhibits good corrosion resistance in high-temperature fluorinated hydrogen gas, hydrochloric acid, and hydrofluoric acid solutions containing oxygen and oxidants and in wet chlorine gas at room temperature.
Alloy 625 is a high-strength material with excellent fatigue resistance. Alloy 625LCF is a derivative brand of Alloy 625, specifically used for corrugated pipes, and has excellent low cycle and heat fatigue resistance. Like alloy 600, alloy 625 can be a corrosion-resistant and heat-resistant material. Alloy 625’s excellent high-temperature strength and comprehensive properties of resistance to halogen corrosion, oxidation resistance, and carburization make it an ideal material for chemical and petrochemical equipment operating in harsh high-temperature environments.
The “C” alloy series alloy C-276 is an excellent alloy material used in the chemical industry to cope with highly corrosive medium conditions (beyond the capabilities of stainless steel). It has outstanding corrosion resistance to various acids, acidic salts, and other types of corrosive chemicals. Alloy C-276 performs excellently in harsh environments such as wet chlorine and hypochlorite. Due to the high molybdenum content of alloy C-276, it has good corrosion resistance to pitting and crevice corrosion caused by chloride ions. The process of seeking materials with better metallurgical and corrosion resistance than alloy C-276 has promoted the development and commercialization of several patented “C” series alloys, including alloys C-22, 622, 59, 686, and C-2000. The molybdenum content of these alloys is roughly the same, while the chromium content is significantly higher than that of alloy C-276. Some brands also contain tungsten or copper.
Ni-Cr-Mo-Cu alloy can resist both nitric acid and sulfuric acid corrosion and has good corrosion resistance in some oxidation-reduction mixed acids.
Ni-Cr-Fe-Mo “G” series alloys
The corrosion resistance of alloy G-3 exceeds that of alloy 400, alloy 600, and alloy 825 in many applications. This alloy is particularly resistant to sulfuric acid and impure phosphoric acid corrosion and can withstand reducing and oxidizing medium conditions. Later developed alloys G – and G-35 had better welding performance and improved corrosion resistance, especially in the weld seam’s heat-affected zone.
Nickel Titanium alloy
Nickel titanium alloy has shape retention properties with shape memory properties. By forming a shape from this alloy at a higher temperature and deforming it from the formed shape at a lower temperature, the alloy will remember its initial shape. Once heated to this so-called transition temperature, it will re-form the shape. By controlling the composition of the alloy, the transformation temperature can be changed. These alloys have superelastic properties and can be used, among other purposes, to provide seismic shock absorbers to help protect stone buildings.
Nickel based wear-resistant alloy
The main alloying elements are chromium, molybdenum, and tungsten, and also contain small amounts of niobium, tantalum, and indium. In addition to its wear resistance, it also has good oxidation resistance, corrosion resistance, and welding performance. It can be used to manufacture wear-resistant components or as a coating material, which can be coated on the surface of other substrate materials through surfacing and spraying processes.
Nickel-based composite powders include self-fluxing alloy powders and non self fluxing alloy powders.
Non self fluxing nickel-based powder refers to nickel-based alloy powder that does not contain B, Si or has a low content of B or Si. This powder type is widely used in plasma arc spraying coatings, flame spraying coatings, and plasma surface strengthening, mainly including Ni Cr alloy powder, Ni-Cr-Mo alloy powder, Ni-Cr-Fe alloy powder, Ni-Cu alloy powder, Ni-P and Ni-Cr-P alloy powder, Ni-Cr-Mo-Fe alloy powder, Ni-Cr-Mo-Si high wear resistant alloy powder, Ni-Cr-Fe-Al alloy powder, Ni-Cr-Fe-Al-B-Si alloy powder, Ni-Cr-Si alloy powder, Ni-Cr-W based wear resistant and corrosion resistant alloy powder, etc.
They add an appropriate amount of B and Si to nickel alloy powder forms nickel based self fluxing alloy powder. The so-called self-fluxing alloy powder, also known as low eutectic alloy, is a series of powder materials formed by adding alloy elements (mainly boron and silicon) that can form low melting point eutectic in nickel, cobalt, and iron-based alloys. Commonly used nickel based self fluxing alloy powders include Ni-B-Si alloy powder, Ni-Cr-B-Si alloy powder, Ni-Cr-B-Si Mo, Ni-Cr-B-Si-Mo-Cu, high molybdenum nickel based self fluxing alloy powder, high chromium molybdenum nickel based self fluxing alloy powder, Ni-Cr-W-C based self fluxing alloy powder, high copper self fluxing alloy powder, tungsten carbide dispersed nickel based self fluxing alloy powder, etc.
Nickel based precision alloy
Including nickel-based soft magnetic alloys, nickel-based precision resistance alloys, and nickel based electric heating alloys. The most commonly used soft magnetic alloy is a permalloy containing about 80% nickel, which has high maximum and initial permeability and low coercivity and is an important iron core material in the electronic industry. The main alloying elements of nickel-based precision resistance alloys are chromium, aluminum, and copper. This alloy has high resistivity, low resistivity temperature coefficient, and good corrosion resistance and is used for making resistors. Nickel-based electric heating alloy contains 20% chromium, which has good oxidation and corrosion resistance and can be used for a long time at temperatures ranging from 1000 to 1100 ℃.
Nickel based shape memory alloy
Nickel alloy containing 50 (at)% titanium. Its recovery temperature is 70 ℃, and its shape memory effect is good. A small change in the proportion of nickel and titanium components can cause the recovery temperature to change within the range of 30-100 ℃. It is commonly used for manufacturing automatic opening structural components used in spacecraft, self-excited fasteners used in the aerospace industry, and artificial heart motors used in biomedicine.
The above constitute several categories of nickel-based alloys; hoping to help you to learn about corrosion knowledge and high-temperature material selection of nickel-based alloys. Follow this platform’s “Special Steel 100 Seconds” to learn more about special steel knowledge.

Application fields of nickel based high-temperature alloys

Nickel based alloys are used in many fields, such as:

• 1. Oceans: Marine structures in the marine environment, desalination, aquaculture, and heat exchange of seawater.
• 2. Environmental protection field: flue gas desulfurization devices for thermal power generation, wastewater treatment, etc.
• 3. Energy field: atomic power generation, comprehensive utilization of coal, tidal power generation, etc.
• 4. Petrochemical industry: refining, chemical equipment, etc.
• 5. Food industry: salt making, soy sauce brewing, etc. Among the many fields mentioned above, ordinary stainless steel 304 is not competent, and in these special fields, special stainless steel is indispensable and irreplaceable. In recent years, with the rapid development of the economy and the continuous improvement of the industrial level, more and more projects require higher grade stainless steel. With the increasing demand for nickel based alloys in various industries. In 2011, the market size of nickel based alloys in China reached 23.07 billion yuan, with a year-on-year growth rate of 19.47%. Therefore, the development level of the industry is steadily increasing.

Classification	Alloy	Features	Applications
Corrosion Resistant Alloys	Alloy 200	Good mechanical properties, Excellent corrosion resistance to many corrosive media	Production facilities for foods, caustic soda, chemicals and synthetic fibers, Electrical and electronic components
	Alloy 201	Excellent cold workability, No embrittlement by carbon above 300℃	Similar applications to Alloy200, Cold deep-drawn parts
	Alloy 400	High strength, Good workability, Excellent corrosion resistance to many corrosive environments	Facilities of seawater desalination, salt production and oil refining, Marine construction coverings, Heat exchangers
	Alloy K-500	Similar corrosion resistance to Alloy400, Higher strength than Alloy400, Completely non- magnetic even at -100℃	Parts requiring higher strength than Alloy400, Oil-drilling tools, Corrosion resistant valves and springs, Rotary pumpshafts, Fasteners
	Alloy 600	Good oxidation resistance at high temp. , Corrosion resistance to pure water/alkali/Cl – ion (SCC*)	Equipment for chemical and food production, Heat exchangers, Electronic components
	DSA 760	High hardness equivalent to that of martensite stainless steel, High corrosion resistance, Non magnetic	Medical scissors, Dental drills, Automotive turbo parts
	Alloy 625	High strength without heat treatment, Excellent corrosion resistance in a wide range of severe corrosive environments	Chemical product manufacturing facilities, Aerospace parts, Seawater treatment facilities
	Alloy C-276	Excellent corrosion resistance in a wide range of severe corrosive environments, Good weldability	Flue-gas desulfurization equipment (FGD), Chemical industrial equipment, Pulp and paper mill facilities
	Alloy 22	Excellent acid corrosion resistance to many types of corrosion such as SCC, pitting and intergranular corrosion	Chemical manufacturing equipment, Combustion gas FGD, Bleaching equipment at paper mills
	Alloy CB3	Excellent acid corrosion resistance to many types of corrosion such as pitting, crevice corrosion and intergranular corrosion	Chemical and petrochemical product manufacturing equipment parts (tanks, heat exchangers, piping system, pumps, valves)
	Alloy 25-6MO	Corrosion resistance to pitting, crevice corrosion and non-oxidizing acids such as sulfuric acid and phosphoric acid	Tubes for petrochemical industry and seawater cooling equipment, Salt production plant parts, Biochemical equipment parts
	DSP5	Similar strength to martensitic stainless steel , Excellent corrosion resistance to non-oxidizing acid	Bellows, Automotive parts , Various sealing parts

• *SCC(Stress Corrosion Cracking)

Suppliers of nickel alloys offer them in a variety of form factors which commonly include:

• Angles
• Balls
• Steel Pipe
• Tubing
• Bars
• Billets
• Ingots
• Channels
• Coils
• Wire
• Rods
• Sheets
• Plates
• Strips
• Flanges
• Forgings
• Pipe fittings

Preparation methods of nickel based high-temperature alloys

The deformation process of high-temperature alloys

Deformed high-temperature alloys are the first high-temperature alloys used in aviation engines and are currently the most widely used and diverse type of high-temperature metal materials. Deformed high-temperature alloys are a type of high-temperature material supported by plasticity and heat treatment such as forging, rolling, roughening, and cold drawing. They are mainly used in turbine discs and can be roughly divided into five generations according to the usage temperature of turbine discs.
1) The design of alloy composition, melting, processing, and heat treatment processes have become the core battlefield for improving the performance of deformed high-temperature alloys.
The traditional “experiment correction” experimental method is no longer suitable for alloy composition. The rapid development of numerical simulation results in a low degree of deformation and alloying of high-temperature alloys, so the design of alloy composition in the early stages of development is crucial. Currently, there are more than ten types of elements in high-temperature alloys, which can be divided into three categories: the first type is the elements that prioritize the formation of austenite with good plastic properties, including Ni, Co, Fe, Cr, Mo, W, V, etc; The second type, entering the matrix to form γ’ elements of phase strengthening phase, including Al, Ti, Nb, Ta, etc; The third type is elements with variable atomic diameters that often aggregate at grain boundaries, leading to grain boundary segregation, such as Pb and Sn. The principle of alloy composition design mainly lies in controlling the precipitation of harmful phases and promoting the generation of favorable phases to ensure the high-temperature strength of high-temperature alloys. With the development of high-temperature alloys, theories and databases for optimizing the performance of various elements are becoming increasingly perfect, and relevant models have been established, such as electron hole theory and phase calculation, d-electron alloy theory, and new camera calculation, multiple linear regression, and artificial neural networks. These have laid a solid foundation for computer-aided design of deformed high-temperature alloy components while reducing the number of actual experiments to reduce alloy costs.
2) In terms of smelting technology, the triple process has gradually become the mainstream method
Usually, deformed high-temperature alloys with a high alloying degree are melted into electrode rods in a vacuum induction furnace and then removed from the vacuum induction melting electrode by electroslag remelting to improve the purity and provide dense and defect free electrodes for subsequent vacuum consumable furnaces, thereby improving the stability of the remelting process and reducing the macroscopic segregation of the alloy. This method has gradually become the main measure for expanding the ingot shape, eliminating macroscopic defects, and improving the quality of high alloy deformation alloys.
3) In terms of deformation technology, compared to casting and machining, the alloy produced by forging has better comprehensive performance
The deformation process of high-temperature alloys is a process in which the alloy undergoes plastic deformation under external forces to form profiles, blanks, and parts with a certain shape, size, and mechanical properties. It can be divided into cold and hot processing, with some using warm processing. In terms of cold processing, it mainly refers to wire drawing, cold drawing of pipes, and cold rolling of thin plates. Hot processing includes forging, welding, etc. It can mainly refine grain size uniform structure and eliminate casting defects, greatly improving the mechanical properties of high-temperature alloys. Among them, forging hot processing technology is the main means of deforming high-temperature alloys. With the increasingly stringent downstream application environment, the strength requirements for deformed high-temperature alloys have become more stringent, thus adding.
The total amount of elements increases, and the organizational structure becomes more complex, resulting in an increase in the deformation resistance of parts during processing, which brings great difficulties to the forging process.
In terms of heat treatment, the correct process can maximize the effectiveness of the alloy.
The chemical composition and microstructure are the key factors that determine the performance of alloys. After the alloy composition, melting process and deformation process are determined, the alloy performance often still cannot meet the requirements. The heat treatment process is the final means of supplementation. However, a reasonable heat treatment process inevitably requires a deep understanding of the alloy’s composition, phase stability, and performance requirements, especially nickel based high-temperature alloys, which are difficult to control (adjust) grain size during the heating process. Therefore, the heat treatment process is the key to building a deformation high-temperature alloy moat.

Casting process of high-temperature alloys

The use temperature of cast high-temperature alloys with the same composition is 10 to 30 ℃ higher than that of deformed high-temperature alloys. Cast high-temperature alloys are directly poured or directionally solidified into parts after remelting of alloy ingots, as they can be precision cast or directionally solidified.
The process is directly formed, so there is no need to consider forging deformation performance. The total amount of alloy elements is significantly higher than that of deformed alloys, and the endurance, tensile strength, and service temperature are significantly improved. According to solidification methods, it can be divided into three categories: equiaxed crystal casting high-temperature alloys, directional solidification high-temperature alloys, and single crystal high-temperature alloys.
1) Equiaxed crystal high-temperature alloys are formed and cast using ordinary precision casting methods. The microstructure is mainly composed of equiaxed crystals of varying sizes, with a small amount of columnar crystals in local areas.
In the 1950s, equiaxed crystal cast high-temperature alloys developed rapidly, and there emerged alloys such as IN100, B1900, and MAR-M200 with excellent performance that are still widely used today. The development of cast high-temperature alloys in China began in the mid-1950s and went through a stage of development from imitation to originality and improvement. The equiaxed crystal cast high-temperature alloy is named the “K” series in the national unified form. Equiaxed high-temperature alloy integral structural castings are widely used in aviation, aerospace, and ground gas engines. Compared with large and complex structural components welded or connected to multiple sheet metal parts, direct forming with precision casting technology has significant economic value.
From the development history of equiaxed grain high-temperature alloys, melting technology is the most crucial, with the main purpose of reducing grain size to improve the fatigue life, tensile strength, and durability of high-temperature alloys.
The fine-grained process, combined with hot isostatic pressing and heat treatment, has gradually become the main process for equiaxed high-temperature alloys.

• Thermal control method: The technical key points are to control the overheating temperature, pouring temperature, and shell temperature of liquid metal and to properly select hot isostatic pressing parameters and heat treatment processes. The equipment and process personnel requirements are high, and the barriers are high. The current new process is to use magnetic fields to suppress metal nucleation during the pouring process;
• Mechanical methods include electromagnetic stirring, ultrasonic vibration, and mechanical rotary vibration methods. In China, the rotary method is the main method, which requires high requirements for process personnel and high barriers;
• Chemical method: The technical key lies in selecting appropriate refining agents while considering the dosage and timing of addition. It does not require additional equipment investment compared to thermal control, mechanical, and other methods. It is an efficient and low-cost process method, but it requires high requirements for process personnel and research and development capabilities, with extremely high barriers.

2) Directionally solidified columnar grain high-temperature alloy is a high-temperature alloy prepared by directional solidification technology, where the grain boundaries are parallel to the main stress axis, thereby eliminating harmful transverse grain boundaries.
Directional solidification can produce alloys with low modulus oriented columnar crystals parallel to the longitudinal axis, thus significantly improving the materials’ creep, plasticity, and thermal fatigue properties. Compared to other types of cast high-temperature alloys, the directional solidification method has a faster process flow, higher yield, and lower testing costs, so it has great potential for development.
According to the principle of directional solidification, the quality of an alloy depends on whether the alloy can be directionally solidified to obtain a planar solidification group.
Weaving, therefore, solidification equipment and heat treatment process are crucial.
In terms of solidification equipment, the shell moving and liquid metal cooling methods are the main casting processes. The core of directional solidification technology is to improve the temperature gradient at the solid-liquid interface; developing equipment process parameters and auxiliary modules is crucial.
In terms of the heat treatment process, solid solution + aging treatment is the most commonly used process, with two objectives: to reduce or eliminate segregation and to increase the number of strengthening phases. Therefore, selecting process parameters such as solid solution temperature, aging temperature, and time is the most crucial.
3) Single crystal high-temperature alloys are high-temperature alloys that eliminate all grain boundaries through directional solidification technology.
Early single crystal high-temperature alloys showed no differences in creep, thermal fatigue, and oxidation resistance compared to directionally solidified columnar crystal alloys, in addition to improvements in transverse properties and plasticity. Moreover, their cost could have been higher, resulting in a slower pace of research. Until the 1970s, when the database of related elements and properties became increasingly perfect, combined with solid solution treatment processes, the temperature bearing capacity of single crystal high-temperature alloys continued to break through.
The preparation of single crystals belongs to directional solidification, and in addition to alloy composition design, solidification equipment, and heat treatment process are also crucial.
In alloy composition design, the core element for improving the performance of single crystal high-temperature alloys is the TCP phase. The amount and distribution of Re and Ru elements added are very important to their morphology. However, these two elements are rare, limiting the number of experiments. Numerical simulation has become the main means.
In terms of solidification equipment, compared to directional solidification technology, the requirements for single-crystal solidification are more stringent. Therefore, how to modify the shell method equipment to improve temperature gradient and control heat flow has become a challenge.
Heat treatment process: Strengthening the mechanical properties relative to high-temperature alloys is very important. Therefore, improving reasonable process parameters such as solution temperature, aging time, and recrystallization temperature is crucial.

Powder Metallurgical Process of High Temperature Alloys

Powder high-temperature alloys can overcome the mechanical property fluctuations in cast high-temperature alloys. Powder high-temperature alloys are high-temperature alloys prepared using powder metallurgy technology. Compared to previous casting forging high-temperature alloys, powder metallurgy technology can, to some extent, solve problems such as component segregation, uneven structure, deterioration of thermal process performance, and forming difficulties in alloy ingots. With the increasingly complex composition of high-temperature alloys and the increasing size of parts, powder metallurgy has become the most important preparation process for aviation engine turbine discs.
The key to the quality of high-temperature alloys is the powder-making and solidification processes. Although the technical routes of powder high-temperature alloys vary from country to country, they generally include steps such as pure smelting of the parent alloy, powder preparation, and treatment, solidification process (hot isostatic pressing densification, hot extrusion, forging forming), heat treatment and testing, among which powder preparation and treatment, and solidification process are the core processes.

Spray forming method for high-temperature alloys

Traditional ingot metallurgy methods can produce almost all shapes of nickel-based high-temperature alloy parts. Still, their severe segregation and coarse grain size problems prompt people to seek other forming methods. The spray-forming process, which originated from powder metallurgy technology and has gradually formed and improved in the past 20 years, is receiving increasing attention from people. The basic principle of spray forming technology is to use high-speed inert gas to atomize molten metal into dispersed small-sized droplets directly deposited on a metal deposition device and welded together to form a highly dense preform with a certain shape quickly. The main advantage of this forming method is that the rapid heat loss during the atomization process eliminates macroscopic segregation and grain coarseness; the inert atmosphere reduces the appearance of harmful inclusions such as surface oxides. In addition, this process is a near net forming method with high production efficiency. Therefore, spray-forming technology has broad application prospects in high-temperature alloys.

Machining of nickel based alloy cutting materials

High-speed steel

High-speed steel (HSS) is used for machining nickel based alloys because it has high toughness and is suitable for intermittent cutting situations such as milling, threading, broaching, and stamping. When processing nickel based alloys, the cutting speed is generally 5-10m/min. According to the toughness of high-speed steel, the feed rate is generally between 0.1 and 0.16mm per tooth.

Hard alloy

Carbides are composed of metal carbides (usually tungsten carbide), which are embedded in soft metal bonding phases and belong to composite materials. When machining nickel based alloys with hard alloy cutting tools, the cutting speed is usually relatively low, ranging from 20-40m/min. Higher cutting speeds can lead to rapid overloading of the cutting material and, therefore cannot be used in a process-safe manner in most cases.

Boron nitride

In addition to diamond, cubic boron nitride (cBN) is the second hardest material. It is harder, more wear-resistant, and more expensive than ceramics. Due to the characteristics of cBN, high cutting speeds can be used during the turning process. CBN is not used for nickel based alloy milling. However, it is used for turning Inconel 718. The recommended cutting speed is between 400m/min and 600m/min. Compared directly with TiAlN-coated hard alloy tools, cBN has a 100% longer tool life at a cutting speed of vc 50m/min. Regarding precision machining under unstable working conditions, cBN is the preferred choice for industry applications.

Ceramics

Ceramics are made by sintering ceramic powder without the need for adding adhesives. DIN ISO 513 divides ceramics into five categories:

• CA=ceramic, mainly composed of aluminum oxide (Al₂O₃);
• CM=composite ceramic, mainly composed of aluminum oxide (Al₂O₃) and other oxide components;
• CN=silicon nitride ceramic, mainly composed of silicon nitride (Si₃N₄);
• CR=Whisker reinforced ceramic, ceramic, mainly composed of aluminum oxide (Al₂O₃);
• CC=Ceramic, all of the above, but coated.

Ceramic tools can still maintain their hardness at high temperatures, which is evident when milling heat-resistant superalloys (HRSA). Compared to hard alloy cutting tools, it can achieve a speed of approximately 20 or 30 times.
Ceramic cutting materials originate from turning processes. The thermal load remains relatively stable during the turning process. During milling, the temperature on the cutting edge may change due to intermittent cutting. The sudden change from frictional heat to cooling causes deformation of the cutting edge. No coolant is used when milling with ceramic cutting edges to prevent thermal shock during tool cooling. SiAlON ceramics (silicon aluminum oxide nitrides) are usually less sensitive to temperature changes than whisker-reinforced ceramics, which is why they are a better choice for milling processing.
The prerequisite for using ceramic cutting edges for milling is a high-speed milling machine. In some cases, this milling machine can accelerate the spindle to over 10000rpm, which is another challenge for the tool.
Although tool systems with ceramic indexable blades can be obtained in various forms on the market and used in the industrial field, milling tools with tool diameters less than 16mm have yet to become popular due to the above reasons. There has been no alternative to cutting tools made of high-speed steel and hard alloy for a long time.
In addition to chemical wear caused by temperature, ceramic cutting materials usually form chip deposits: metal vapor is generated in the heat generated in the processing area, which is released when fused with the surface of the cutting material – a part of the ceramic will peel off.

Selection guide for nickel-based alloys

Nickel alloy combines excellent corrosion resistance, strength, toughness, metallurgical stability, processability, and weldability. Many nickel alloys also have excellent heat resistance, making them an ideal choice for applications that require high temperature strength and chemical corrosion resistance at high temperatures.

Corrosion resistance

To ensure the selection of materials in chemical equipment design, corrosion resistance should be the top consideration.

Corrosion forms

The common types of high-temperature chemical corrosion are briefly described below. Due to the strong resistance of nickel alloys to hydrogen corrosion, hydrogen corrosion is omitted.

• (1) Oxidation: Oxidation is the most common form of corrosion at high temperatures, characterized by the formation of metal oxidation corrosion products. These so-called oxide scales are usually very dense and have strong adhesion, thus slowing down further corrosion. However, the oxide skin can be penetrated or peeled off under extremely harsh conditions. Chromium is the most important element that endows alloys with antioxidant properties. Just like in the case of stainless steel, adding a small amount of aluminum, silicon, and rare earth elements can further improve the stability and adhesion of oxides, especially under thermal cycling conditions. The stable oxide skin not only slows further oxidation, but also serves as an effective screen wall to resist other types of corrosion.
• (2) Sulfurization: Sulfurization produces oxide skin rich in metal sulfides. Reducing vulcanization environments are usually more corrosive than oxidizing vulcanization atmospheres. Nickel based alloys are more prone to sulfurization than stainless steel due to their ability to form low melting point nickel sulfide. Like oxidation, the addition of chromium can significantly improve the sulfurization resistance.
• (3) Chlorination: Stainless steel can rapidly corrode when exposed to high-temperature chlorine gas and chlorine compounds. Due to the highly unstable nature of iron chloride and chloride oxides, severe chlorination processes may occur without significant oxide skin formation. Nickel based alloys have much stronger chloride resistance than iron alloys and are ideal materials for chlorine or chloride environments.
• (4) Carburization: In a high-carbon active atmosphere, carbon often diffuses into the metal matrix and forms metal carbides. This form of corrosion is called carburization, which can cause serious damage to mechanical properties, especially plasticity and impact strength. Nickel based alloys exhibit excellent resistance to carburization, as nickel, unlike iron, is not a strong carbide-forming element.
• (5) Nitriding: Nitriding refers to the diffusion of nitrogen into the metal lattice to form metal nitrides. This phenomenon is mainly encountered in high-temperature ammonia atmospheres in the chemical industry. Like carburization, the damage manifests as embrittlement rather than metal loss. Nickel does not form nitrides, so nickel-rich alloys have excellent resistance to nitriding.
• (6) Internal corrosion: Carburization and nitriding are by no means the only high-temperature degradation modes of materials characterized by internal damage. All high-temperature corrosion is diffusion-driven, characterized by erosion below the surface, mainly along grain boundaries. This applies to oxidation and vulcanization, especially halogenation. Internal corrosion often penetrates deeper into the metal interior than the surface metal loss. Therefore, the evaluation of high-temperature corrosion should not only be based on thickness or metal loss but also rely on metallographic examination.

Let’s look at the corrosion rate of several Hastelloy alloys in the medium.

Table.4 Corrosion Rate of Hastelloy Alloy (mm/year)

Metal material	B-2	B-3	C-276	C-22	G	G-30	316L
1% hydrochloric acid boiling	＜0.03	–	0.25	＜0.07	–	–	Complete corrosion
10% hydrochloric acid boiling	0.18	0.13	7.3	10	–	–	Complete corrosion
10% sulfuric acid boiling	0.05	0.05	0.58	0.28	0.48	–	Complete corrosion
Boiling with 10% nitric acid	Complete corrosion	Complete corrosion	0.43	0.02	0.02	0.02	0.05
99% acetic acid boiling	＜0.01	­-	＜0.01	0.001	–	0.03	0.1
88% acetic acid boiling	0.02	–	0.04	＜0.03	0.15	0.04	0.48
85% phosphoric acid boiling	0.63	–	0.51	2.4	0.64	–	16.4
2% fluoric acid 50 ℃	0.22	–	0.15	0.08	–	0.04	5.3

Note:

• The test time is 24 hr.
• In short, please note that the corrosion resistance is relative.

The use of nickel alloy symbolizes the improvement of traditional stainless steel’s ability to resist various acids, alkalis, and salts. The outstanding advantage of nickel alloys is their excellent corrosion resistance in aqueous solutions containing halide ions. In this regard, nickel alloy is significantly superior to austenitic stainless steel, which is known to be susceptible to corrosion from chloride and fluoride aqueous solutions. The excellent corrosion resistance of nickel alloys proves that they have lower metal loss and can withstand local corrosion, especially resistance to pitting or crevice corrosion, intergranular corrosion, and stress corrosion cracking. The formation of these localized corrosions further dilutes uniform corrosion, which is the main cause of failure caused by corrosion in chemical factories.

The corrosion resistance of nickel alloys is partially attributed to the inherent low activity of nickel compared to iron, as its oxidation potential is measured to be much higher in the electromotive force (EMF) sequence than iron. Like stainless steel, chromium-nickel alloys have passivation ability (i.e., spontaneously forming an ultra-thin but highly adhesive surface oxide layer that effectively prevents corrosion).
Another advantage of nickel is its ability to combine with many alloy elements without forming brittle phases. Generally, alloying elements such as Cr, Mo, Cu, etc. are added to improve corrosion resistance.
The comparison of resistance levels of nickel alloys in ordinary chemical factory environments is shown in Table 5. These general guidelines do not represent specific purposes and are only used as a reference for selection.
Table.5 General Guidelines for Corrosion Resistance of Nickel Alloys

Alloy Materials	200	400	600	625	690	825	G-3	C-276	B-2
Sulphuric Acid	▲	●	▲	●	▲	●	●	●	●
Phosphoric Acid	▲	▲	▲	●	●	●	●	●	●
Hydrochloric Acid	▲	▲	■	●	▲	▲	▲	▲	●
Hydrofluoric Acid	●	●	▲	●	●	■	●	●	●
Nitric Acid	■	■	▲	●	●	●	●	▲	■
Organic Acids	●	●	●	●	●	●	●	●	●
Strong Alkali	●	●	●	●	●	▲	●	●	●
Reducing Salt	●	●	●	●	●	●	●	●	●
Oxidizing Salt	■	■	▲	●	●	▲	●	●	■

● The representative is very good, good;
▲ Represents good and satisfactory;
■ Not recommended.

Metallurgical stability

Another important characteristic considered in selecting alloys for high-temperature applications is metallurgical stability, also known as thermal stability, which refers to the ability of materials to resist the formation of brittle microstructure phases or precipitation during aging (i.e., long-term exposure at high temperatures). The so-called “aging brittleness” mainly manifests as a decrease in plasticity and toughness, which may also decrease corrosion resistance.

Although some alloys, such as 600 and 601, do not undergo age embrittlement, most alloys suffer varying degrees of damage, with alloy 625 being one of them. When exposed to temperatures ranging from 1200 ℉ (649 ℃) to 1400 ℉ (760 ℃), plasticity and impact strength significantly decrease. These properties are partially restored at higher temperatures due to the re-dissolution of brittle precipitates. Equipment failure due to reduced plasticity and toughness is not common, thanks to the high initial performance of nonaging treated nickel alloys.

Chemical resistance

The most common form of corrosion in high-temperature chemical processing environments is gas-phase corrosion, especially oxidation, sulfurization, and halogenation (chlorination and fluorination). Other forms of performance degradation in harsh, high-temperature environments are mainly carburization, nitriding, and hydrogen corrosion. Due to the absence of metal loss and surface pits, these corrosion forms do not belong to traditional corrosion but mainly manifest as damage to metallurgical, and mechanical properties – the most common being embrittlement.

The effects of chromium, molybdenum, cobalt, tungsten, silicon, and aluminum can be beneficial and harmful, depending on specific exposure conditions, especially temperature and reducing or oxidizing atmospheres.

Several modes of material performance degradation may occur simultaneously. For example, many industrial environments contain oxygen and chlorine, and metals are exposed to chlorine oxidation conditions and suffer from deadly corrosion. Liquid phases such as molten salt, ash, or molten metal can also cause abnormally severe corrosion. These corrosive substances are rarely encountered during chemical processing, and we will not discuss them.

Welding guide

Most nickel alloys are welded by manual arc welding (SMAW), gas shielded tungsten arc welding (GTAW), and gas shielded metal arc welding (GMAW). The plasticity of nickel alloy weldments is very good, and their low thermal expansion characteristics reduce residual stress and deformation. Generally, only post-weld heat treatment of precipitation hardening stainless steel is required. The technical conditions for nickel alloy electrodes and wires specified by the American Welding Society (AWS) are shown in Table 6.
Table.6 AWS technical conditions for welding materials

Alloy materials	Welding electrode	Filler metal
200	ENi-1	ERNi-1
400	ENiCu-7	ERNiCu-7
600	ENiCrFe-3	ERNiCrFe-3
625	ENiCrMo-3	ERNiCrMo-3
G-3	ENiCrMo-9	ERNiCrMo-9
G-30	ENiCrMo-11	ERNiCrMo-11
C-276	ENiCrMo-4	ERNiCrMo-4
C-22	ENiCrMo-10	ERNiCrMo-10
622	ENiCrMo-10	ERNiCrMo-10
686	ENiCrMo-14	ERNiCrMo-14
59	ENiCrMo-13	ERNiCrMo-13

The welding method of nickel alloy is very similar to that of austenitic stainless steel. However, due to the particularly slow solidification of the nickel-rich weld pool and poorer penetration, products with full penetration welds may require joint form and welding technology modifications. Nickel alloys are less likely to contain pollutants that may cause weld embrittlement than steel materials.

The comprehensive properties of high plasticity, low expansion, and tolerance for the dissolution of different metal elements have made nickel-rich welding consumables suitable for welding different metals. This includes not only welding nickel-based alloys to iron based alloys but also welding stainless steel to carbon steel and alloy steel. Similarly, nickel alloys can be deposited onto the surface of carbon steel without the risk of cracking.

Welding characteristics and requirements of nickel and nickel based alloys

Welding characteristics of nickel based alloys

• (1) Liquid weld metal has poor flowability. Nickel based alloys cannot improve the flowability of weld metal by increasing the welding current like steel weld metal. If the current is increased, it can actually have a harmful effect. This is the inherent characteristic of nickel based alloys. Due to the poor flowability of weld metal, it is not easy to flow to both sides of the weld seam. Therefore, in order to achieve good weld formation, the swing process is sometimes used, But this swing is small and large, which can easily cause undercut. To eliminate this defect, the welder should pause slightly when swinging to the extreme position on each side, in order to have enough time to fill the melted weld metal with undercut. In addition, the welding arc should be as short as possible.
• (2)  The inherent characteristic of nickel based alloys is that the depth of weld metal penetration cannot be increased by increasing the welding current. As mentioned above, excessive current is harmful to welding, causing cracks and pores. Due to the shallow melting depth of the weld metal, the thickness of the blunt edge of the joint should be thinner.

Cleaning before welding

The most important thing for successfully welding nickel- and nickel-based alloys is cleaning. Before welding, the welding groove and the 30 mm range on both sides must be strictly cleaned, especially to remove the surface oxide layer. Because Ni can form brittle elements with P, S, Pb, AI, or low melting point substances during welding. Due to the high melting point of oxides (usually formed above 540 ℃) (2040 ℃) and the low melting point of nickel (1400 ℃), it is easy to cause incomplete fusion. In addition, the main harmful impurities in nickel and nickel-based alloy welding, such as zinc (Zn), sulfur (S), carbon (C), bismuth (Bi), lead (Pb), cadmium (Cd), can increase the welding crack tendency of nickel based alloys; Gases such as oxygen, hydrogen, and carbon monoxide have great solubility in molten nickel, while their solubility greatly decreases in the solid state. The change in solubility is the main cause of porosity in melt welding.

Welding joint form

Due to the poor thermal conductivity, strong adhesion, shallow penetration depth, and high weld seam of nickel and nickel based alloy fusion welding compared to steel, it is easy to form poor fusion between passes and layers. Larger groove angles and smaller blunt edges should be selected to ensure penetration. When welding simultaneously, swing welding should be adopted as much as possible (the width of the swing welding seam should not be greater than 3 times the diameter of the welding rod), and the swing should be stopped slightly on both sides to ensure good fusion.

Control of process parameters

When welding nickel and nickel based alloys, a smaller welding line energy should be selected, and the interlayer temperature should be strictly controlled. Due to the poor thermal conductivity of nickel and nickel based alloys, if the welding current is too high, the arc voltage is too high, the welding speed is slow, and the interlayer temperature is too high, it can easily cause the welding joint to overheat, resulting in coarse grains. At the boundary of the coarse columnar grains, some low melting point eutectic crystals are concentrated, which have low strength and high brittleness and are easy to form cracks under the action of welding stress. These low melting point eutectics mainly include Ni s eutectic, Ni Pb eutectic, Ni NiO and Ni P eutectic, etc. It can be seen that impurities such as oxygen, sulfur, lead, and phosphorus in the weld seam significantly impact the tendency of hot cracking. In addition, the generation of coarse grains can also reduce welded joints’ mechanical and corrosion resistance. Therefore, while ensuring good fusion, choosing a smaller welding current, lower arc voltage, and faster welding speed is best. The welding current must decay during argon arc welding, with a 4-6 seconds decay time. At the same time, the interlayer temperature should be strictly controlled below 150 ℃ (if necessary below 100 ℃) to avoid overheating and thermal cracking of welded joints.

Control of surface formation of nickel and nickel based alloy welds

Nickel and nickel-based alloy welds should be raised as much as possible, naturally formed, and should not be flattened or concave as much as possible. Due to factors such as high surface tension, poor fluidity, high viscosity, and easy oxidation of nickel and nickel based alloy weld metal, naturally formed welds are generally convex. If the weld is flat or concave, cracks may occur due to stress. Therefore, it is best to add a backing plate on the back of the manual arc welding when welding on one side and forming on both sides. In addition to strengthening the gas protection of the front weld during argon arc welding, a gas protection device must be added on the back of the argon arc welding.

Preheating and post weld heat treatment

Nickel and nickel-based alloy welding generally does not require preheating and heat treatment but only considers appropriate preheating and heat treatment during corrosion resistant surfacing.

Common defects and prevention measures

Due to nickel-based materials’ single-phase structure, problems are similar to austenitic stainless steel during welding, such as weld porosity, welding hot cracks, lack of fusion, excessive deformation, undercut, and other defects. In practical production, the commonly encountered and more harmful ones are weld porosity and welding hot cracks.

Table.7 Common Defects and Preventive Measures in Welding of Nickel and Nickel-based Alloys

Defect		Cause	Preventive measures
Stoma		1. Hydrogen, oxygen, and carbon dioxide have great solubility in molten liquid nickel based alloys, while their solubility in solid state is greatly reduced. 2. The oil, moisture, dust, and oxide layer on the welding groove and its sides are not cleaned thoroughly. 3. The welding current and arc voltage are low, the welding speed is too fast, and the welding thermal energy is low. 4. The diameter of the welding gun gas protection nozzle is small, the flow rate of the protective gas is too low, and the gas protection effect is poor. 5. Poor drying of welding rods, insufficient insulation time for drying thermometers.	1. Welding rods or wires containing deoxygenated elements or forming oxides such as aluminum and titanium, which have strong affinity with oxygen and nitrogen and form stable compounds, can reduce porosity. 2. Use a dedicated grinding wheel or stainless steel wire brush to remove the oxide layer from the welding groove and its sides, and use acetone and anhydrous ethanol to remove harmful substances such as oil, moisture, and dust on its surface. 3. Select appropriate welding current, arc voltage, and welding speed, i.e. welding wire energy, for welding to ensure that harmful gases fully escape before the deposited metal solidifies. 4. Select a larger diameter welding gun gas protection nozzle to have sufficient gas protection area for the deposited metal, and select an appropriate gas protection flow rate to have good gas protection effect, preventing harmful gases such as hydrogen, oxygen, nitrogen in the air from invading the molten pool metal. 5. Strictly follow the specified drying temperature and insulation time to dry the welding rod used, and place the welding rod in the insulation cylinder during use
Slag inclusion		1. Welding materials and filler metal are not clean. 2. Poor interlayer cleaning. 3. The welding current is too low.	1. Use chemical and mechanical methods to remove groove and welding wire oil and oxide film. 2. Use appropriate current.
Unfused		1. The groove shape is unreasonable. 2. There are residual oxides. 3. Welding current is too low or welding speed is too high.	1. Increase the angle of the groove. 2. Use chemical and mechanical methods to remove the oxide film. 3. Increase the welding current appropriately.
和ot cracking	Crystallization crack	The low melting eutectic liquid film state remaining at the grain boundary is distributed on the surface of the grain, causing the separation of the grain boundary and forming crystal cracks under the tensile stress generated by cooling shrinkage.	Strictly control the content of S, P, and Si.
	Liquefaction crack	The formation mechanism of liquefaction cracks is essentially the same as that of crystallization cracks, both of which are due to the cracking of brittle and hard low melting eutectic phases between grains under high-temperature stress. The only difference is that crystallization cracks are formed during the solidification process of liquid weld metal, while liquefaction cracks are formed after the solid base material remeltes the grains under the peak temperature of thermal cycling.

Weld porosity

Causes of weld porosity

• (1) Oxygen, hydrogen, and carbon dioxide gases have great solubility in molten liquid nickel-based alloys, while their solid-state solubility greatly decreases. During the welding process of nickel based alloys, when the gas cools from high temperature to low temperature, the solubility of the gas in the deposited metal also decreases. The free gas cannot completely escape and form pores in liquid nickel with poor fluidity before the nickel based alloy weld solidifies.
• (2) The oil, moisture, dust, and oxide layer on the welding groove and its sides must be cleaned thoroughly.
• (3) The welding current and arc voltage are low, and the welding speed is too fast. The welding heat energy is low.
• (4) The diameter of the welding gun gas protection nozzle is small, the flow rate of the protective gas needs to be higher, and the gas protection effect could be better.
• (5) Poor drying of welding rods and insufficient insulation time for drying thermometers.

Preventive measures for weld porosity

• (1) Welding rods or wires containing deoxygenated elements or forming oxides (such as aluminum and titanium, which have strong affinity with oxygen and nitrogen and form stable compounds) can reduce porosity.
• (2) Use a dedicated grinding wheel or stainless steel wire brush to remove the oxide layer from the welding groove and its sides. Use acetone and anhydrous ethanol to remove harmful substances such as oil, moisture, and dust on its surface.
• (3) Select the appropriate welding current, arc voltage, and welding speed, i.e., welding wire energy, for welding to ensure that harmful gases fully escape before the deposited metal solidifies.
• (4) Select a larger diameter welding gun gas protection nozzle to have sufficient gas protection area for the deposited metal, and select an appropriate gas protection flow rate to have a good gas protection effect, preventing harmful gases such as hydrogen, oxygen, nitrogen in the air from invading the molten pool metal.
• (5) Strictly follow the specified drying temperature and insulation time to dry the welding rod, and place the welding rod in the insulation cylinder during use.

Welding Hot Cracks

Causes of Welding Hot Cracks

• (1) Weld thermal embrittlement is caused by mixing sulfur, lead, phosphorus, or low melting point eutectic crystals, which form intergranular films and cause severe embrittlement at high temperatures. Hot cracks in weld metal are generally caused by the infiltration of low melting point inclusions from the surface along the intergranular boundaries.
• (2) The dirt on the welding groove and its two sides cannot be cleaned thoroughly, and the sulfur in the oil often causes hot cracks in the nickel based alloy weld seam.
• (3) The uneven surface of the weld seam causes stress concentration and cracks.
• (4) When the arc is stopped, the arc crater is not filled, and the current decay time is short. The amount of deposited metal at the end of the arc is small, and the strength of the arc crater is relatively weak. Under the action of phase change stress and confinement stress, microcracks are generated at the end of the arc.
• (5) The welding current is too high, the welding speed is slow, the welding line energy is large, and the interlayer temperature is too high, causing the welding joint to overheat and produce coarse grains. Some low melting point eutectic crystals are concentrated on the boundaries of the coarse grains, which have low strength and high brittleness. Under welding stress, they are easy to form hot cracks.

Preventive Measures for Welding Hot Cracks

• (1) Select nickel based alloy welding materials with low sulfur and phosphorus content to prevent the generation of low melting point inclusions in the deposited metal.
• (2) The dirt and oxide layer on the welding groove and both sides must be cleaned to prevent sulfur, lead, phosphorus, or low melting point impurities from mixing into the deposited metal.
• (3) The surface of the weld seam should be uniform and flat. No local unevenness or unevenness exists to prevent cracks from occurring due to local stress concentration. The formation of nickel based alloy welds is best achieved by natural forming with uniform protrusions.
• (4) When closing the arc, the method of filling the arc crater multiple times must be adopted to fill the crater evenly. During argon arc welding, the current decay time should be long, and the current decay should be minimized to ensure no depressions at the end of the arc.
• (5) The selected welding current, arc voltage, and welding speed must be appropriate, that is, to choose a smaller welding line energy and lower interlayer temperature as much as possible while ensuring good fusion to prevent overheating of the weld and heat-affected zone from generating thermal cracks.

Specific operational requirements

Weld cleaning

• (1) Weld cleaning groove, blunt edge, and 30mm range on both sides of the weld bead.
• (2) Clean the oxide film at the weld seam with a file or grinding wheel.
• (3) The welding seam’s dirt, grease, and paint should be cleaned with acetone, an alkaline solution, or a special synthetic agent.

Welding precautions

When welding, to ensure good penetration and fusion, try to use small welding line energy, short arc, no swing, or small swing operation methods within the range of process parameters.
When multiple layers of welding are required for thicker welded parts, the following regulations should be met:

• (1) Multi-pass welding should be used for all welding layers except for backing welding.
• (2) The temperature inside the layer should be less than 100 ℃.
• (3) After each layer and weld, the slag on the weld surface should be thoroughly removed, and various surface defects eliminated.
• (4) The welding joints of each layer and each layer should be staggered.

When using solid core welding wire or tungsten argon arc welding without filling wire, the back of the weld seam should be filled with argon, and internal protection should be implemented. Internal protection measures can be taken by using two methods: overall or partial argon filling of the pipe, and the following requirements should be met:

• (1) At the beginning of argon filling in the pipe, the flow rate can be appropriately increased, and welding can only be carried out after confirming that the air inside the pipe is completely discharged.
• (2) The flow rate of argon gas during welding can be gradually reduced to avoid high argon gas pressure causing incomplete penetration of the inner or root of the weld during forming.

During tungsten argon arc welding, the heating end of the welding wire should always be under argon protection. An auxiliary conveying protective gas towing cover can be installed behind the welding nozzle to enhance the protective effect.
Arc scratches are strictly prohibited on the surface of the weldment, and it is strictly prohibited to start or stop the arc on the surface of the weldment.
The welding power ground wire connected to the welding component should not directly contact the workpiece. It should be connected using materials of the same material as the welding component to avoid iron pollution.
During welding, the quality of arc striking and arc stopping should be ensured, and the arc crater of arc stopping should be filled up.
When welding welds made of materials with small pipe diameters and a high tendency for hot cracking, measures such as installing cooling copper blocks on both sides of the weld or wiping both sides of the weld with cold water or ethanol should be taken to reduce the high-temperature residence time of the weld and accelerate the cooling speed of the weld.
After welding, the slag on the surface of the welding seam and the surrounding splashes must be cleaned promptly, as well as the anti-splashing materials.
To avoid pollution during welding construction, stainless steel hammers, stainless steel wire brushes, and specialized grinding wheels should be used.

Environmental conditions

The environmental conditions for nickel and nickel alloy welding construction should meet the following requirements:

• (1) The ambient temperature shall not be lower than 0 ℃;
• (2) The wind speed during manual arc welding shall not exceed 8m/s, and the wind speed during argon arc welding shall not exceed 2m/s;
• (3) The relative humidity shall not exceed 90%;
• (4) No rain or snow weather.

Welding method 

• (1) Use argon arc welding for butt welds with a pipe diameter of 3 “or less or a wall thickness of less than 6mm; Otherwise, argon arc backing and welding rod arc welding are used to fill the cover surface;
• (2) The welding seam of the connecting pipe with penetration requirements shall be covered by argon arc welding with a backing electrode, and the welding seam of the nonpenetration connecting pipe shall be welded by arc welding with a welding rod.

Positioning welding

• (1) When using solid wire tungsten argon arc welding for positioning welding, the back of the weld seam should be protected with argon filling;
• (2) The length of the positioning welding is l0-15mm, the height is 2-4mm, and it does not exceed 2/3 of the wall thickness;
• (3) The number of welding points for pipeline positioning welds is 2-5. Before welding, both ends of the positioning weld should be ground into a slope for easy arc striking;
• (4) The sequence of tack welding should be staggered from top to bottom, and when spot welding the saddle opening, two sharp points should be spot welded first;
• (5) The baffle and matching tools should be the same material as the base material.

Weld repair

• (1) After removing defects, the cleaned weld seam should be ground to a slope of at least 1:3;
• (2) Use a grinding machine to remove defects; the root defect grinding width should be 4-5mm. After removing the defect, groove repair should be done on the repaired part. The angle on both sides of the groove should be greater than 25., The angle at both ends of the grinding groove shall not be less than 45.;
• (3) After repairing the weld seam, it is still inspected according to the original regulations;
• (4) The number of repairs to the same part shall not exceed two. If an additional repair is required, measures shall be formulated and approved by the technical director of the construction unit;
• (5) The location, frequency, and testing results of welding repairs should be recorded and archived.

In short, do a good job of pre-welding cleaning. To ensure good fusion, choose a smaller welding line energy, strictly control the interlayer temperature, choose a larger groove angle and smaller blunt edges, and try not to make the weld flat or concave. In addition, while implementing appropriate welding processes, strict management is also necessary during the construction process to ensure the welding quality of nickel and nickel based alloy welds.

Understand the characteristics of alloys

Here is a summary of the main characteristics of each alloy introduced, which affect the suitability of the material in high-temperature corrosive environments in chemical plants.

• Alloy 600 has excellent oxidation resistance, chlorination resistance, carburization resistance, and nitriding resistance, but its sulfurization resistance is poor. Alloy 600 is widely used in high-temperature chlorine/hydrogen chloride and ammonia environments.
• Alloy 601 has excellent resistance to carburization and periodic oxidation, with moderate strength but excellent thermal stability. Alloy 601 is widely used in polluting combustion environments.
• Alloy 617 combines excellent high-temperature strength, thermal stability, oxidation resistance, and carburization resistance, making it suitable for producing nitric acid and petrochemical products.
• Alloy 625 has high strength and excellent comprehensive corrosion resistance, including corrosion resistance in aqueous media. It has excellent fatigue fracture resistance but moderate thermal stability. Alloy 625 is widely used in chemical/petrochemical equipment.
• Alloy X combines outstanding strength, workability, oxidation resistance, carburizing resistance, and nitriding resistance. It is a good alloy used as a stressed component in corrosive combustion environments.
• Alloy 214 has excellent oxidation resistance [up to 2200 ℉ (1204 ℃)], chlorination resistance, carburization resistance, and nitrogen resistance, moderate thermal stability, workability, and welding performance. It is an alloy suitable for extremely corrosive environments, with limited product form and quantity.
• Alloy 230 has the best balance of strength, thermal stability, fatigue fracture resistance, oxidation resistance, and workability, making it suitable for high-strength parts in harsh combustion environments.
• Alloy 242 is a nickel-based alloy with the best fluorine and fluoride corrosion resistance. It has very high strength and good thermal stability. Alloy 242 is unsuitable for temperatures above 1500 ℉ (816 ℃). It is commonly used in the production of fluorinated polymers.
• Alloy 333 has excellent oxidation resistance and carburization resistance, as well as good sulfurization resistance and mechanical properties. It can be used in various chemical/petrochemical equipment.
• Alloy 45TM is the best choice for applications requiring comprehensive chlorination/oxidation/vulcanization/carburization resistance. This alloy is suitable for incineration and gasification processes.
• Alloy 602CA has outstanding resistance to periodic oxidation (up to 2200 ℉ (1204 ℃)) and carburization and excellent resistance to oxidation/sulfurization gases. At very high temperatures, it has high creep strength.

Considering cost factors

Nickel based alloys are about 2 to 5 times more expensive than 310 stainless steel in terms of price. Due to the small difference in processing and manufacturing costs between nickel-based alloys and stainless steel, the price difference is greatly reduced from the perspective of installation costs.
Another important consideration in economic analysis is the higher performance, lower maintenance costs, and longer service life of high-performance materials. From the life cycle cost analysis perspective, nickel-based alloys are often proven to be the most economical choice.

How to Choose the Right Nickel Alloy Manufacturer?

Key Considerations When Choosing a Nickel Alloy Manufacturer

In the ever-evolving landscape of industrial manufacturing, selecting the right nickel alloy manufacturer is a pivotal decision that can significantly impact your products’ quality, performance, and longevity. Choosing a manufacturer requires a comprehensive evaluation of various critical factors that extend beyond the surface. This guide delves into the key considerations that should be at the forefront of your decision-making process, ensuring a successful collaboration that aligns with your business goals.

Expertise and Experience: Building on a Foundation of Knowledge

The foundation of a reputable nickel alloy manufacturer lies in their expertise and experience. An experienced manufacturer’s in-depth understanding of metallurgy allows them to create alloys tailored to your specific requirements. Years of working in the industry grant them insights into refining their production processes and optimizing the quality of the alloys they produce.

Quality Standards and Certifications: Elevating Assurance

A hallmark of a top-tier nickel alloy manufacturer is its commitment to quality standards and certifications. Look for manufacturers that adhere to internationally recognized quality management systems, such as ISO 9001. Certifications like these underscore a manufacturer’s dedication to consistency, traceability, and continuous improvement, giving you peace of mind regarding the products you receive.
Customization Capabilities: Your Unique Needs Addressed
The ability of a manufacturer to offer customization plays a pivotal role in your decision-making process. Opt for a manufacturer that embraces customization capabilities, enabling them to create alloys that meet your specific mechanical, thermal, and corrosion-resistant requirements. This ensures that the final product is tailored to your application’s demands.
Material Variety: Exploring Options for Efficiency
A comprehensive manufacturer should offer various nickel alloys to cater to industry needs. Material variety opens avenues for innovation and ensures that you can choose the ideal alloy for your intended application without compromise.
Production Capacity: Meeting Demands Efficiently
Scalability is a crucial aspect, especially if your production demands vary. Choose a manufacturer with a substantial production capacity, accommodating both small-scale and large-scale orders without compromising lead times or quality.

Researching Potential Manufacturers: Navigating the Selection Process

Online Research: A Wealth of Information at Your Fingertips
The internet serves as a valuable resource for researching potential nickel alloy manufacturers. Look for manufacturers with a strong online presence that showcases their capabilities, certifications, and client testimonials. An informative website reflects a manufacturer’s commitment to transparency and communication.
Industry Networks and Recommendations: Tapping into Collective Wisdom
Leverage industry networks and seek recommendations from professionals within your field. Networking can provide invaluable insights into manufacturers with a proven track record of delivering exceptional nickel alloys.
Reviewing Client Feedback: Gauging Real-world Experiences
Client feedback offers a window into the real-world experiences of working with a manufacturer. Reviewing testimonials and case studies helps you assess a manufacturer’s strengths and potential areas for improvement.

Assessing Quality and Testing Procedures: Ensuring Excellence

Quality Control Processes: A Rigorous Approach to Consistency
A manufacturer’s commitment to quality extends to their quality control processes. Look for those that employ stringent quality checks throughout the production cycle, guaranteeing consistency and performance.
Testing Equipment and Facilities: Investing in Precision
Modern manufacturing demands cutting-edge technology. A manufacturer equipped with advanced testing equipment and facilities can provide accurate assessments of alloy properties, ensuring they meet your specifications.

Communication and Collaboration: The Pillars of Success

Responsiveness and Clarity: A Transparent Partnership
Open communication is vital throughout the manufacturing process. A manufacturer’s responsiveness to your inquiries and ability to provide clear, concise information reflects their dedication to a transparent and successful partnership.
Material Traceability
Material traceability is crucial, especially in industries with strict regulatory standards. A manufacturer that can provide detailed documentation of the materials used and their origins showcases transparency and accountability.
Technical Support: Navigating Complexities with Expertise
The complexities of nickel alloy manufacturing may require additional technical support. Choose a manufacturer that offers technical assistance to address any challenges, fostering a smoother collaboration.
Logistics and Timely Delivery: From Production Floor to Your Door
Location Considerations: Proximity for Efficiency
The location of your manufacturer can impact logistics and delivery times. Opt for a manufacturer strategically located to ensure timely and efficient delivery of your nickel alloy products.
Supply Chain Efficiency: A Well-Orchestrated Process
A manufacturer’s commitment to supply chain efficiency streamlines the entire production cycle. Efficient supply chain management ensures you receive your products on time and in optimal condition.

Cost-effectiveness and Value: Balancing Investment

Comparing Price vs. Quality: A Delicate Balance
While cost is critical, prioritize the balance between price and quality. Comparing prices against the manufacturer’s reputation, certifications, and product performance is essential for making an informed decision.
Long-term Cost Considerations: Sustainability Pays Off
Consider the long-term costs associated with product quality and durability. An alloy that commands a higher initial investment but offers superior longevity may prove more cost-effective in the long run.
Environmental and Ethical Practices: Supporting Responsible Manufacturing
Sustainable Manufacturing: A Greener Footprint
In an era of environmental awareness, choose a manufacturer that embraces sustainable manufacturing practices. Opting for environmentally friendly processes aligns with responsible business practices.
Ethical Standards: A Commitment to Morality
A manufacturer’s ethical standards are indicative of its commitment to corporate responsibility. Look for manufacturers that adhere to ethical sourcing practices, supporting fair labor and responsible resource utilization.

Case Studies: Successful Collaboration

Industry Examples: Learning from Excellence
Case studies provide insight into successful collaborations between manufacturers and their clients. Industry examples illustrate how manufacturers’ capabilities translate into real-world achievements.
Making Your Decision
Choosing the right nickel alloy manufacturer is a multifaceted process that demands meticulous consideration of various critical aspects. You can forge a partnership that propels your business forward by prioritizing expertise, quality, customization, and ethical values.
In industrial manufacturing, selecting a nickel alloy manufacturer is a decision that reverberates throughout your business operations. The nuances of this decision must be considered, as they impact the quality, performance, and reputation of your products. By adhering to the outlined considerations, you can confidently navigate the landscape of nickel alloy manufacturers, ensuring a collaboration that aligns with your vision and requirements.

Why Choose Us?

At Yaang, we embody all the attributes of an ideal nickel alloy manufacturer. With over [X years] of experience, we have consistently delivered premium nickel-based alloys to diverse industries. Our commitment to quality is unwavering, and our products undergo rigorous testing to meet the highest industry standards. Our extensive product range caters to various applications, and our expert engineers are ready to collaborate with you on custom solutions.
We prioritize material traceability and provide comprehensive documentation to assure our clients of the origins and quality of our alloys. Our technical support team is dedicated to offering insightful guidance, making your alloy selection process seamless. With a global presence, we ensure timely deliveries worldwide.

Conclusion

In your quest for the right nickel alloy manufacturer, remember that making an informed decision can significantly impact your project’s success. Consider factors such as expertise, product range, quality control, customization abilities, material traceability, technical support, and global reach. With these considerations in mind, you’re well-equipped to partner with a manufacturer that meets your nickel alloy needs and enhances your project’s overall efficiency and reliability.