A Comprehensive Guide to Nickel-based super alloy: Incoloy 330 (UNS N08330/W.Nr. 1.4886)

What is Incoloy 330?

Incoloy 330 (UNS N08330) is a nickel-iron-chromium austenitic alloy, specially used in high temperature environment Oxidation and carburization. The nickel content of 34%-37% makes the material highly resistant to chloride stress corrosion cracking and sigma phase precipitation embrittlement. The material is processed through standard processing procedures for stainless steel and nickel alloys. It is widely used for anti-corrosion in the environment of combined heating and carburizing.

Designated as UNS N08330 or DIN W.Nr. 1.4886, Incoloy 330 (also known as “Alloy 330”) is an iron-nickel-chromium alloy with deliberately controlled addition of silicon to improve its oxidation resistance. It has a solid solution composition and is not hardenable by heat treatment. The high nickel and chromium contents provide excellent resistance to oxidation and carburization. Alloy 330 has very good high-temperature strength and corrosion resistance, as well as excellent workability and weldability. It is mainly used for industrial heating furnaces, muffles, flare tips, alloy gridss, bar baskets, gas turbine components, boiler fixtures, and other high-temperature components.

ASTM B535 UNS N08330 seamless pipes after preliminary rolling, 219.1mm(O.D)x13.6mm(W.T), Incoloy Alloy 330.

Chemical Composition Requirements of Incoloy 330 (UNS N08330/W.Nr. 1.4886)

The Chemical Composition of Incoloy 330, %
Nickel	34.0-37.0
Chromium	17.0-20.0
Iron	Balance
Carbon	≤0.08
Silicon	0.75-1.50
Manganese	≤2.00
Phosphorus	≤0.030
Sulfur	≤0.030

Physical Properties of Incoloy 330 (UNS N08330/W.Nr. 1.4886)

Density		Melting Range		Specific Heat	Permeability
g/cm3	lb/in3	°F	°C	J/kg.°C	@ 200 oersteds
8.08	0.292	2520-2590	1380-1420	460	1.02

Mechnaical Properties of Incoloy 330 (UNS N08330/W.Nr. 1.4886)

Tensile Strength		Yield Strength		Elongation
Mpa	ksi	Mpa	ksi	%
552-621	80-90	221-290	32-42	35-45

Mechanical properties in annealed state at room temperature

Ultimate tensile strength, ksi (MPa)	80-85 (552-586)
0.2% conditional yield strength, ksi (MPa)	30-43 (207-296)
Two inches elongation%	40-45
Hardness, Rockwell B grade	70-85

High temperature mechanical properties, tensile properties of annealed materials

Incoloy 330 (N08830) nickel-based alloy specific heat:

• (1): 0.11 BTU/lb/°F (32-212 °F) (British heat/lb/Fahrenheit). 
• (2): 460 Joules/kg/°C (0-100°C) (Joules/kg/°C). 

Incoloy 330 (N08830) nickel-based alloy permeability:

• 1.02 at 70°F/20°C (RT). 

Product Forms and Standards

Product Form	Standard
Bars and shapes	ASTM B511
Billets and bars	ASTM B512
Seamless pipes and tubes	ASTM B535, B829
Weld pipes and tubes	ASTM B546, B710, B739
Plates, sheets and strips	ASTM B536
Welded fittings	ASTM B366
Forgings	SAE AMS 5716

Application areas of nickel-based alloy incoloy 330 (UNS N08330/W.Nr. 1.4886)

• Heating pipes, containers, baskets and chains used in sulfuric acid pickling plants.
• Sea water cooling heat exchanger, marine product pipeline system, acid gas environment pipeline.
• Heat exchanger, evaporator, washing, dip tube, etc. in phosphoric acid production.
• Air heat exchanger in petroleum refining.
• Food engineering, chemical process.
• Flame retardant alloy for high pressure oxygen application.
• Heat exchange tubes
• Pipe fittings
• Flanges
• Valves

Incoloy 330 (N08830) nickel-based alloy linear average coefficient of thermal expansion

Incoloy 330 (N08830) nickel-based alloy electric heating characteristics

Temperature	Thermal conductivity			Resistivity
°F	°C	Btu.in/ft2.h.°F★	Watt/meter/degree Celsius	Micro ohm cm	Microohm.m
75	twenty four	86	12.4	612	1.017
400	204	108	15.6	649	1.079
800	427	134	19.3	688	1.144
1200	649	162	23.4	721	1.199
1600	871	198	28.6	744	1.237
1800	982	216	31.2	749	1.245

Remarks: Btu.in/ft².h.°F refers to the heat directly conducted per hour per square foot or per inch of material under each degree of temperature difference in Fahrenheit. Heat is the British thermal unit Btu (1btu is the energy required to heat 1 pound of water to 1 degree Fahrenheit). 

Corrosion resistance of Incoloy 330 (N08830) nickel-based alloy

Incoloy 330 (N08830) has excellent corrosion resistance, especially for oxidation, carburization and nitriding environments Has corrosion resistance. In an aqueous environment, the chromium component of 330 can resist corrosion in an oxidizing environment, and the nickel component can enhance the resistance to reduction corrosion. The high nickel content of the alloy makes the material quite resistant to chloride stress corrosion cracking and sigma phase embrittlement. 

Oxidation resistance of Incoloy 330 (N08830) nickel-based alloy

Incoloy 330 (N08830) has excellent oxidation resistance, and has good anti-scaling ability under the conditions of 2000°F (1095°C). Any oxide scale will adhere tightly to the surface of the material after it is formed, especially under conditions of alternating cold and heat cycles. 

Carburization resistance of incoloy 330 (N08830) nickel-based alloy

35% nickel and a certain amount of silicon make the material have excellent carburization resistance. Under the alternate environment of carburization and oxidation, Alloy 330 exhibits excellent resistance to “green rot”. 

Heat treatment of Incoloy 330 (N08830) nickel-based alloy

Incoloy 330 (N08830) is an austenitic stainless steel, which cannot be hardened by heat treatment. Only by cold working can it be hardened and reach room temperature strength. For most high-temperature applications, 330 is not annealed after cold forming or welding. If the material needs to be fully annealed, it should be done in the temperature range of 1870-2050°F (1020-1120°C). The best creep resistance can be obtained by water quenching the material, but rapid cooling to below 800°F (425°C) can also achieve the same effect. 

Manufacturing of Incoloy 330 (N08830) nickel-based alloy

Incoloy 330 (N08830) alloy can be hot or cold formed using standard procedures for austenitic stainless steel and nickel alloys. The work hardening rate of the alloy can be compared with other austenitic stainless steels. It is recommended to process the material in a room temperature environment. If the material needs thermal processing, the material should be evenly heated to 2050-2150°F (1120-1180°C), and then reduced to 1750¼°F (950°C) for heat preservation. The material should be cooled quickly with water quenching. 
We recommend annealing treatment after hot working to ensure the best corrosion resistance and the best grain structure of the material. The material cannot be forged or bent in the range of 1200-1600°F (650-870°C) because the ductility of the material is low in this temperature range, which will cause the intergranular structure of austenitic alloy materials to crack. 

Welding of Incoloy 330 (N08830) nickel-based alloy

Incoloy 330 (N08830) can be welded by tungsten arc, electrode welding and plasma arc processing, and the corrosion resistance obtained by tungsten arc welding is the best. Before welding, the material should be annealed and kept clean and free of dirt, grease and other impurities. Grinding should be done within one inch of both sides of the joint. The temperature between welding layers cannot exceed 300°F (150°C), and no heat treatment is required before or after welding. Alloy 330 can be welded into different types of metals.

Variety specifications and supply status of Nickel-based super alloy: Incoloy 330 (UNS N08330/W.Nr. 1.4886)

Variety classification

Yaang Pipe Industry can produce various specifications of Incoloy 330 seamless pipe, Incoloy 330 steel plate, Incoloy 330 round bar, Incoloy 330 forgings, Incoloy 330 flange, Incoloy 330 pipe fittings, Incoloy 330 welded pipe, Incoloy 330 steel strip, Incoloy 330 wire and supporting welding materials.

Delivery status

• Seamless pipe: solid solution + acid white, length can be set;
• Plate: solid solution, pickling, trimming;
• Welded pipe: solid solution acid white + RT% flaw detection;
• Forging: annealing + car polish; Bars are forged and rolled, surface polished or car polished;
• Strips are delivered after cold rolling, solid solution soft state, and deoxidized;
• Wire rods are finely ground in solid solution pickled disk or straight strips, solid solution straight strips Delivery in light state.

High temperature corrosion resistance of RA330 alloy

RA330 (Incoloy 330, Alloy 330, UNS N08330) alloy is a nickel-iron-chromium heat-resistant alloy used to make heat-insulating walls for gas heating furnaces. The corrosion performance of RA330 alloy at high temperatures was investigated by analyzing its surface oxidation pattern after 2160h of continuous operation at 850°C. The results show that the surface in contact with coal is very corrosive, and the corrosion resistance of RA330 alloy is very high. The results show that the surface in contact with coal is mainly coal ash formation of molten salt corrosion, the oxide film is incomplete, the surface of the formation of pits; with the gas contact surface is mainly high temperature oxidation corrosion, the oxide film is more complete, sulfur corrosion is not obvious.
RA330 alloy is a nickel-iron-chromium system heat-resistant alloy by adding a certain amount of silicon elements to give it a better high-temperature strength. The aerospace, petrochemical, and chemical metallurgy industry is increasingly widely used because it has high temperature strength and excellent resistance to high temperature oxidation and corrosion resistance. Coal dry distillation refers to the process in which coal is heated and decomposed under air-isolated conditions to produce coke (or semi-coke), coal tar, coal gas, and other products. Due to the process of low-temperature pyrolysis of low-temperature coal using high-temperature gas, the gas heating furnace heats the gas into the furnace body distillation section of the coal pyrolysis; the gas contains water vapor, a small amount of H₂S, and other corrosive gases, it is required to make the heating furnace material has better resistance to high-temperature corrosion performance. In this paper, RA330 alloy is used to make heat insulation walls of coal gas heating furnaces to study its corrosion resistance in high temperature environments.

1. Test

1.1 Sample preparation

The use of RA330 alloy production of gas heating furnace heat insulation wall, specimens into the pyrolysis furnace dry distillation section of the gas distribution device, specifications for the 6.4mm × 100mm × 70mm. 850 ℃ high temperature gas, through the mixing chamber’s dry distillation section into the refractory furnace dry distillation section. The refractory furnace, continuous operation of 2160h, takes off RA330 alloy specimens into the laboratory to detect corrosion resistance, in which the gas composition is analyzed. The composition of the gas was analyzed as shown in Table 1.
Table.1 Composition of coal gas (% by volume)

H2	CO	CO2	H2O	N2	H2S
5	5	30	20	39.95	0.05

1.2 Testing and analyzing method

The Japanese Keyence VHX-600 stereo microscope observed the macroscopic morphology and the fracture morphology was observed by Dutch Philips XL-30W/TMP scanning electron microscope. Cross-sectional specimens were cut near the fracture, and metallographic samples were made after inlaying, polishing, and etching. Using German Leica DMI5000M metallographic microscope and scanning electron microscope to observe the metallographic organization, German OBLF-750QSN emission spectrometer to determine the basic chemical composition, the United States EDAX Phoenix X-ray spectrometer to determine the chemical composition of the micro-region, Japan Rigaku D/MaxUItimax + X-ray diffractometer to determine the outer surface layer of the physical phase The structure was determined by Rigaku D/MaxUItimax+ X-ray diffractometer.

2. Results and Discussion

2.1 Surface macroscopic observation and analysis

The macroscopic morphology of the contact surface of RA330 with coal and gas are shown in Fig. 1 and Fig. 2, respectively, which is rougher on the contact surface with coal and smoother on the contact surface with gas.

Figure.1 Macroscopic morphology of the surface in contact with coal

Figure.2 Macroscopic morphology of the gas contact surface

2.2 Surface microscopic observation and analysis

Scanning electron microscope observation shows that the RA330 specimen has a rough surface in contact with coal; the main components are O, Cr, Fe, and Ni, containing a certain amount of C, O, S, Na, Mg, Si, Ca, K, Al and other elements, which are the ash of the coal after combustion. The surface in contact with gas is smooth, mainly composed of O, Cr, Fe, and Ni, containing a certain amount of sulfur. Sample and coal, gas contact surface morphology, and film energy spectrum are shown in Figure 3-4.

Figure.3 The microscopic morphology of the surface in contact with coal (a) and the EDAX spectra of the film layer (b)

Fig.4 Microscopic morphology (a) and EDAX spectrum (b) of the surface in contact with coal gas

2.3 Surface phase analysis

The phase structure of the surface coverings of RA330 specimen in contact with coal and gas is mainly Cr₂O₃ and (Fe, Cr)₃O₄ phases, and the rest of the spectral peaks are basic γ-Fe, and no sulfide peaks appeared. There is a diffuse amorphous peak in the range of 20°-30° in the XRD spectrum of the surface in contact with coal, which is mainly amorphous carbon and ash, but there is no such peak on the surface in contact with coal gas. The XRD patterns of the surface coverings in contact with coal and gas are shown in Fig. 5 and Fig. 6, respectively. There is no sulfide peak in the surface coverings of RA330, indicating less sulfide in the surface coverings and better anti-sulfidation performance.

Figure.5 XRD pattern of the surface in contact with coal

Figure.6 XRD spectrum of the surface in contact with coal gas

2.4 Cross-sectional microanalysis

The cross-section of the RA330 specimen in contact with coal is shown in Fig. 7(a), and the chemical composition of corrosion products is shown in Fig. 7(b). The depth of the pits varies; most of them are 30-40 μm, and the inner surface of the pits is angular and fragmented, with no protective film layer on the surface. The morphology (cross-section) of the depression on the surface in contact with coal is shown in Fig. 8, and it is observed that there is residual ash on the surface, the surface contour of the ash is smooth, and no obvious oxidized film layer is found. The common elements in coal ash are Si, Fe, S, Na, Mg, Si, Ca, K, Al, etc. The composition of the compounds is relatively complex, mainly containing SiO₂, Al₂O₃, CaO, MgO, and Fe₂O₃, because the low-melting-point compounds in the coal ash will be in the molten state at high temperatures, in which sulfide and Na₂SO₄ have lower melting points. Lower, they are attached to the metal surface, it will make the protective oxide film form dissolution damage, while the diffusion of oxygen ions through the molten salt speeds up the rate of local formation of pore corrosion; the surface covering layer contains a large amount of carbon, the oxide film has a certain reduction effect, destroying the stability of the oxide film; carbon and chromium to form carbide, or diffusion into the grain, resulting in the formation of larger internal stress between the grains, in the intergranular corrosion conditions, the formation of metal surface fragmentation.

Figure.7 Morphology of the surface pits in contact with coal (a) and the chemical composition of corrosion products (b)
The morphology (cross-section) of the corrosion layer on the surface of the RA330 specimen in contact with coal gas and the rupture and regeneration of the oxide film layer are shown in Figs. 9 and 10, respectively. It is observed that the oxide film on the surface is relatively intact, and the ruptured oxide film can form a new oxide film, which in turn slows down the corrosion process of the metal substrate. There are no pits and fragmentation on the surface. However, the subsurface has a certain internal oxidation corrosion layer depth of 20-40 μm. The occurrence of internal oxidation is mainly due to the high-temperature environment, oxygen, sulfur, and carbon dissolved in the alloy, and the reaction of the elements in the alloy, and then in the alloy sub-surface layer of the generation of internal oxides precipitation, dispersed in the formation of the internal oxidation zone in the metal phase. Internal oxidation can occur simultaneously with external oxidation or separately.

Figure.8 Morphology of the surface depression in contact with coal (cross-section)

Figure.9 Morphology of corrosion layer on the surface in contact with gas (cross-section)

Figure.10 Oxide film regeneration at rupture

3. Conclusion

• (1) The high-temperature corrosion on the surface of RA330 in contact with coal is mainly the corrosion of molten salt formed by ash at high temperatures; the oxide film is incomplete, and etching pits are formed on the surface.
• (2) The high-temperature corrosion on the surface of RA330 in contact with coal gas is mainly high-temperature oxidative corrosion, and sulfur corrosion is not obvious. The surface formed Cr₂O₃ and (Fe, Cr)₃O₄ spinel-like oxides. The oxide film is relatively complete; even if the surface oxide film ruptures, the rupture can form an oxide film layer, slowing down the corrosion process of the metal substrate.
• (3) The sub-surface corrosion process of RA330 in contact with coal and gas is gentle, and the corrosion depth is shallow.

Author: Shi Changjiang