A Comprehensive Guide to Nickel-based super alloy: Inconel X-750 (UNS N07750/W.NR 2.4669)

What is Inconel X-750?

Designated as UNS N07750 or W. Nr. 2.4669, Inconel X750, also known as “Alloy X750”, is a nickel-chromium alloy similar to Inconel 600 but made precipitation hardenable by additions of aluminum and titanium. The alloy has good resistance to corrosion and oxidation along with high tensile and creep-rupture properties at temperatures up to about 1300°F(700°F). Its excellent relaxation resistance is useful for high-temperature springs and bolts. The Inconel X-750 can also be used in gas turbines, rocket engines, nuclear reactors, pressure vessels, tooling, and aircraft structures.

Inconel X-750 alloy is mainly a nickel base superalloy aged with γ′ [Ni3 (al, Ti, Nb)] phase. It has good corrosion resistance and oxidation resistance below 980 ℃, high strength below 800 ℃, good relaxation resistance below 540 ℃, and good formability and weldability. The alloy is mainly used to make annular parts, structural parts and bolts with high strength and corrosion resistance, plane spring and coil spring with medium or low stress and relaxation resistance working below 540 ℃. It can also be used to manufacture turbine blades and other parts.

Characteristics of Inconel X-750 (UNS N07750/W.NR 2.4669)

• Iron-Nickel-Chromium based alloy hardened by precipitation of elements aluminium and titanium. 
• Good corrosion resistance and oxidation resistance even at high temperatures to 980 °C, 
• Good mechanical strength until 800 °C, 
• Good relaxation resistance until 540 °C,
• Good processability and weldability,
• Excellent mechanical properties in low temperature environment. 

Chemical Composition of Inconel X-750 (UNS N07750/W.NR 2.4669)

C	Cr	Ni+Co	Fe	Mn	Si	S	Al	Ti	Co	Cu	Nb+Ta
≤0.08	14.0-17.0	≥70.0	5.0-9.0	≤1.0	≤0.5	≤0.01	0.4-1.0	2.25-2.75	≤1.0	≤0.5	0.7-1.2

Mechanical Properties of Inconel X-750 (UNS N07750/W.NR 2.4669)

Density		Melting Range		Curie Temperature,°F	Magnetic Permeability, 70°F, 200H	Linear Contraction during Precipitation Treatment(1300°F/20hr), in/in
lb/in3	g/cm3	°F	°C	As hot-rolled	As Hot-Rolled	Hot-Rolled	20% Cold-Rolled	Annealed
0.299	8.28	2540-2600	1393-1427	-225	1.0020	0.00044	0.00052	0.00026

Physical Properties of Inconel X-750 (UNS N07750/W.NR 2.4669)

Density  (g/cm3)	Elastic modulus (GPa)	Melting point (℃)
8.24	204.9	1260~1320
Thermal conductivity (W(m•℃))	Hardness (HBS)	Thermal expansion coefficient( 21 – 93 °C) 10-6×m/m  °C
14.7	346-450	13.0

Product Forms and Standards

Products Form	Standard
Rod, Bar and Forging	ASTM B637, ISO 9723-9725
Plate, Sheet and Strip	ISO 6208
Wire	BS HR 505

Heat treatment system of Inconel X-750 (UNS N07750/W.NR 2.4669)

The temperature of hot strip is 980 ℃ and the temperature of hot strip is 980 ℃. For the intermediate heat treatment system of materials and parts, the following processes can be selected for heat treatment.

• (1) Annealing: 955 – 1010 ℃, water cooling.
• (2) Annealing before welding: 980 ℃, 1H.
• (3) Stress relief annealing: 900 ℃ for 2 h.
• (4) Stress relief annealing: 885 ℃± 15 ℃, 24h, air cooling.

Heat treatment process of inconelx-750 parts

Heat treatment of parts shall be carried out in neutral or reducing atmosphere without sulfur to avoid vulcanization. Parts should be avoided from “hot cold” treatment between 870 ℃ and 650 ℃. For parts with large cross-section, in order to prevent cracks, the parts should be cooled in air after solution treatment. The final heat treatment of finished parts is as follows:
(1) For parts working above 600 ℃ and requiring the best creep resistance:

• Solid solution: 1150 ℃± 15 ℃, holding for 2-4h, air cooling;

• Aging: 845 ℃± 15 ℃, holding for 24h, air cooling + 705 ℃± 15 ℃, holding for 24h, air cooling.

(2) For parts working below 600 ℃ and requiring the best room temperature and high temperature tensile properties:

• Solid solution: 980 ℃± 15 ℃, holding for 1h, air cooling;

• Aging: 730 ℃± 15 ℃, holding for 8h, furnace cooling at 50 ℃ / h to 620 ℃± 10 ℃, holding for 8h, air cooling.

(3) The following heat treatment systems are generally used for annular parts:

• Solid solution: 1095 ℃± 15 ℃, holding for 2-4h, air cooling;
• Aging: 845 ℃± 15 ℃, holding for 24h, air or furnace cooling to + 705 ℃± 15 ℃, holding for 20h, air cooling.

(4) The following systems shall be used for heat treatment of bars and forgings at temperatures below 600 ℃

• Homogenization: 885 ℃± 15 ℃, heat preservation for 24h, air cooling;

• Aging: 705 ℃± 15 ℃, holding 20 ± 1H, air cooling.

(5) Plate and strip in annealed state and plate, strip and wire used for spring can be heat treated with the following system:
Aging:
1) 705 ℃± 15 ℃, holding for 22h, air cooling;
2) 760 ℃± 10 ℃, holding for 1 h, air cooling.

• Solid solution: 980 ℃± 15 ℃, holding for 1h, air cooling;

• Aging: 730 ℃± 10 ℃, holding for 8h, furnace cooling at 50 ℃ / h to + 620 ℃± 10 ℃, holding for 8h, air cooling.

Melting and casting process of Inconel X-750 (UNS N07750/W.NR 2.4669)

The alloy is remelted by arc furnace plus vacuum consumable remelting, vacuum induction plus electroslag, electroslag plus vacuum consumable remelting or vacuum induction plus vacuum consumable remelting.

Process performance and requirements of inconel x-750

• 1. The forming properties of inconelx-750 are as follows: forging temperature of the alloy ranges from 1220 ℃ to 950 ℃. In order to obtain good microstructure and properties of the final forging or bar, the subsequent forging heating temperature should be carried out at the corresponding lower temperature. The final forging temperature should not be lower than 950 ℃. The alloy should be treated by solid solution after vigorous forming.
• 2. Inconel X-750 welding performance: The alloy has good weldability and can be welded in various ways, but it is difficult to weld large section parts, but it is better to weld small section parts and thin plates. The welding must be carried out after annealing or solution treatment, and stress relief treatment should be carried out after welding, and the humidity should be kept at 980 ℃ for 0.5h or 900 ℃ for 2h. After aging treatment, the strength of the welded assembly in the state of approximate complete heat treatment can be obtained.

Thermal performance of Inconel X-750 (UNS N07750/W.NR 2.4669)

Thermal conductivity of Inconel X-750

θ/℃	50	100	300	500	900
λ/（W/（m·℃））	14.7	15.9	20.1	25.1	37.3

Coefficient of linear expansion of Inconel X-750

θ/℃	20-200	20-300	20-400	20-500	20-600	20-700	20-800
α/10-6℃-1	13.1	13.5	14.1	14.4	15.0	15.6	16.2

Welding performance of Inconel X-750 (UNS N07750/W.NR 2.4669)

The alloy has good weldability and can be welded in various ways, but it is difficult to weld large section parts, but it is better to weld small section parts and thin plates. The welding must be carried out after annealing or solution treatment, and stress relief treatment should be carried out after welding, and the humidity should be kept at 980 ℃ for 0.5h or 900 ℃ for 2h. After aging treatment, the strength of the welded assembly in the state of approximate complete heat treatment can be obtained.

Application areas of nickel-based alloy inconel X-750 (UNS N07750/W.NR 2.4669)

• Heat treatment factories with tray,basket and fixture.
• Steel wire annealing and radiant tube, high-speed gas burner,the mesh belt furnace.
• The ammonia reforming in the isolation tank and the catalytic support grid for production of nitric acid.
• Heating pipes, containers, baskets and chains used in sulfuric acid pickling plants.
• Exhaust system components.
• Piping system.
• The solid waste incinerator combustion chamber.
• Pipe supports and ash handling part.
• Exhaust detoxification system components.
• Oxygen to the heater.
• Heat exchange tubes.
• Pipe fittings.
• Flanges.
• Valves.

Variety specifications and supply status of Nickel-based super alloy: Inconel X-750 (UNS N07750/W.NR 2.4669)

Variety classification:

Yaang Pipe Industry can produce various specifications of Inconel X-750 seamless pipe, Inconel X-750 steel plate, Inconel X-750 round bar, Inconel X-750 forgings, Inconel X-750 flange, Inconel X-750 pipe fittings, Inconel X-750 welded pipe, Inconel X-750 steel strip, Inconel X-750 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.

Influence of cooling mode after solid solution on the organization and properties of Inconel X-750 alloy

Nickel-based high-temperature alloy is a kind of high-temperature alloy developed to meet the requirements of modern aerospace technology under various high-temperature use conditions, and advanced aerospace engines have been the most active field showing the vitality of high-temperature alloys. Adjustment of high-temperature alloy performance commonly used means including optimization of alloy composition, adjusting the processing technology and heat treatment process, etc., in order to obtain the matrix organization and precipitated phases, especially the type, size, distribution of precipitated phases, etc. Inconel X-750 nickel-based alloys are commonly used in the heat treatment process: solid solution + aging treatment, the precipitated phases in the process of which is a key factor in determining its performance. The good high-temperature performance of nickel-based high-temperature alloys mainly depends on the microstructure composed of L12-type precipitated phase γ'(Ni3(Al, Ti)) and face-centered cubic nickel-rich matrix. A large number of studies have shown that the shape, size, volume fraction, and spatial arrangement of γ’ are crucial to the properties of the alloy, especially the size and volume fraction of the γ’ phase have a huge influence and thus have received great attention. In recent years, extensive research has been carried out on the effects of the heat treatment process on Inconel X-750 alloy, more studies have been carried out on the solid solution process and aging process; for example, Jeong et al. investigated the effects of precipitation of γ’ phase from X-750 alloy under different aging temperatures and stress relaxation conditions, and Marsh et al. investigated the effects of heat treatment on fracture toughness. Researchers have concentrated on the effects of solid solution treatment and aging on the organization and properties of alloys and less on the effects of solid solution cooling methods on the organization and properties of alloys.
In recent years, it has been found that the solid solution cooling mode seriously affects the precipitation of γ’ phase during solid solution cooling and aging of the alloy. When the cooling rate is faster, the alloy precipitates a single uniformly distributed γ’ phase during solid solution treatment, which has a higher distribution density and is close to a spherical shape. When the cooling rate is small, the alloy precipitates a variety of sizes of γ’ phase in the solid solution cooling process, and its shape also varies greatly. Nickel-based high-temperature alloys, γ’ phase has a great influence on the organization and properties of the alloy. The study of solid solution cooling mode is crucial for the use of Inconel X-750 alloy, so this paper concentrates on the study of solid solution cooling mode on the organization and properties of the Inconel X-750 alloy and mainly concentrates on the study of solid solution cooling mode on the process of γ’ phase precipitation, and solid solution cooling mode on the precipitation and distribution of carbides: carbide precipitation and distribution.

1. Test materials and methods

The test material is Inconel X-750 alloy electroslag ingot smelted by vacuum induction melting + electroslag remelting, formed into forging billet after opening the billet, and samples were taken after forging of forging billet. The sample sizes are as follows: impact specimen Φ10mm × 10mm × 40mm, tensile specimen Φ12mm × 55mm, and phase analyzed specimen Φ15mm × 55mm, and the chemical compositions (mass fraction, %) are 0.05C, 0.2Si, 0.65Mn, 15.5Cr, 2.25Ti, 6Fe, 0.7Al, 0.95Nb, and remaining Ni.
Figure 1 shows the property diagram of Inconel X-750 alloy simulated by Thermo-Cale thermodynamic calculation software, and the precipitation temperature of γ’ phase is around 950°C. Table 1 shows the different heat treatment processes for Inconel X-750 alloy.
The SEM samples were treated by electrolytic polishing + electrolytic corrosion method; the electrolytic polishing solution was 80% methanol + 20% sulfuric acid, 30 V voltage, and corrosion 15-20 s. The electrolytic corrosion solution was 85 mL phosphoric acid + 8 g chromium trioxide + 5 mL sulfuric acid, 5 V voltage, and the corrosion time was 1-3 s. The TEM samples were treated by the conventional electrolytic polishing method, and the electrolytic corrosion solution was a 10% HClO4 aqueous solution. Phase analysis was done by quantitative and particle size analysis, and particle size analysis was done by X-ray small angle scattering particle size analysis.

Figure.1 Phase diagram of Inconel X-750 alloy from Thermo-Cale calculations
Table.1 Heat treatment process of Inconel X-750 alloy

Sample number	Solution	Cooling method	Aging	Cooling method
1	1060 ℃ x 1h	Water-cooling	720 ℃ x 6h	Air cooling
2	1060 ℃ x 1h	Oil cooling	720 ℃ x 6h	Air cooling
3	1060 ℃ x 1h	Furnace cooling	720 ℃ x 6h	Air cooling

2. Experimental results and analysis

2.1 Effect of cooling mode on alloy grain size
Figure 2 shows the grain size of the three alloys; it can be seen that there are carbides inside the crystal and near the grain boundary, and there is no significant difference in grain size.
2.2 Effect of cooling mode on γ’
2.2.1 Effect of cooling mode on γ’ phase during solid solution cooling process
Figure 3 shows the mass fraction of γ’ phase in the alloy under different cooling methods after solid solution treatment. No precipitation of γ’ phase was found in both solid solution water-cooled and solid solution oil-cooled alloys, and the mass fraction of precipitated γ’ phase in solid solution furnace-cooled alloys was 11.064%. In the study by A.R.P. Singh et al., a uniform and fine precipitated phase appeared in the alloy after solid solution water cooling. Compared with other nickel-based high-temperature alloys, the cooling mode is more sensitive to the influence of Inconel X-750 alloy, and water cooling or even oil cooling can inhibit the precipitation of γ’ precipitated phase after solid solution.
Figure 4 shows the morphology of γ’ phase in the alloy after cooling in the solid solution furnace. In Figure 4(a), it is found that uniform large particles of precipitated phase precipitate inside the alloy, with irregular shapes, mostly cubic shapes, small densities, and roughening phenomena, which are labeled as γ’ phase by the transmission diffraction pattern; as shown in Figure 4(b), the fine spherical γ’ phase is found on the grain boundaries, with larger densities; and as shown in Figure 4(c), the tetrahedral and polygonal γ’ phases are found inside the alloy, around which fine γ’ phases are present.
Figure 5 shows the particle size distribution of the γ’ phase in the alloy; the size of the precipitated γ’ phase after cooling in the solid solution furnace of the alloy is 10-60 nm, the number of γ’ phases with the size of 36-60 nm is larger and cubic, and the number of γ’ phases with the size of 10-18 nm is smaller and spherical.
The cooling rate seriously affects the shape of the precipitated phase. In the previous high-temperature alloy research, it was found that the cooling rate after the solid solution is different; the shape of the precipitated phase in the alloy has a big difference; when the cooling rate is faster, the precipitated γ’ phase in the alloy is mostly spherical, and when the cooling rate is slower, the precipitated γ’ phase in the alloy is cubic or lamellar. Fig. 4 shapes of precipitated γ’ phases in alloys are spherical, cubic and polygonal. The cooling rate has a significant effect on the mismatch and elastic strain in the alloy; increasing the cooling rate decreases the mismatch in the alloy, i.e., when the cooling rate is low (furnace cooling), the coherent strain increases due to an increase in the unconfined mismatch. The increase in the unconfined mismatch is all balanced by the compressive elastic strain. This explains well the different shapes of the γ’ precipitated phase for different cooling rates. At the microstructure level, it is mainly manifested as γ’ phase transforms from a simple spherical shape to a complex cubic shape. With the change in secondary morphology, the elastic strain changes, i.e., the primary precipitated phase transforms to a complex shape, which elevates the mismatch within the alloy.

Figure.2 OM images of Inconel X-750 alloy under different cooling methods after solution treatment
(a) water cooling + aging; (b) oil cooling + aging; (c) furnace cooling + aging

Fig.3 Mass fraction of γ’ phase in Inconel X-750 alloy under different cooling modes after solution treatment
2.2.2 Effect of cooling mode on γ’ phase in aging process
Figure 6 shows the SEM images of the alloy with different cooling modes + aging treatment after solid solution. In Fig. 5(a, b) and Fig. 6(a, b), it is shown that uniform and fine γ’ precipitated phases are precipitated inside both solid solution water cooling + aging and solid solution oil cooling + aging alloys. The γ’ phases are regular spherical, with a higher number of γ’ phases with sizes of 5-18 and 5-10 nm. The mass fractions of γ’ phases in the solid solution water cooling + aging and solid solution oil cooling + aging alloys are shown in Fig. 3 to be 7.986% and 8.111%, respectively.
Figure 6(c) fine diffuse spherical γ’ phase precipitated in the cubic-shaped γ’ phase gap in the alloy, the size of the cubic-shaped γ’ phase is 36-60 nm, the larger the cubic-shaped γ’ phase gap, the greater the density of fine spherical γ’ phases, the size of 5-10 nm, comparing Fig. 5(c) and (d), the aging treatment process of the cubic γ’ phase basically did not appear to grow up, and only increase a certain amount of 5-10 nm of fine spherical γ’ phases, and only increase a certain number of 5-10 nm. 10 nm of fine spherical γ’ phase, and its increased mass fraction is 3.604%.
2.3 The effect of cooling speed on carbide
2.3.1 Cooling mode on the solid solution cooling process carbide effect
Although the content of carbides in Inconel X-750 alloy is small, they are mainly distributed at grain boundaries and have a significant impact on the properties of the alloy. The main carbides in Inconel X-750 alloy include MC and M23C6.
Figure 7 shows the TEM image of the carbides of the alloy after solid solution without aging treatment, and Figure 8 shows the EDAX spectrum of the carbides. In Fig. 7(a, b), there are massive carbides on the grain boundaries, which were determined to be Nb- and Ti-rich MC-type carbides by electron diffraction pattern calibration and EDAX analysis. In Fig. 7(c), the presence of larger particles of carbide M23C6 on the grain boundaries, as well as the massive MC phase. Due to the high melting point of the MC phase, no decomposition occurs during the solid solution process, pinning the grain boundaries, resulting in no significant difference in the grain size of the three alloys.

Fig.4 TEM and SEM images of γ’ phase of Inconel X-750 alloy after solid solution furnace cooling

Fig.5 Grain size distribution of γ’ phase in Inconel X-750 alloy
(a) water cooling + aging; (b) oil cooling + aging; (c) furnace cooling; (d) furnace cooling + aging

Fig.6 SEM images of γ’ phase of Inconel X-750 alloy after solid solution + aging
(a) water cooling + aging; (b) oil cooling + aging; (c) furnace cooling + aging

Figure.7 TEM images of grain boundary carbides of Inconel X-750 alloy
(a, d) water cooling; (b, e) oil cooling; (c, f) furnace cooling

Fig.8 EDAX spectrum of grain boundary carbides of Inconel X-750 alloy
2.3.2 Effect of cooling mode on carbides in the aging process
Figure 9 shows the TEM images of grain boundary carbides in the isothermal aging stage of the alloy after solid solution. A kind of needle-like carbide was found on the grain boundary of solid solution water cooling + aging and solid solution oil cooling + aging alloys, which was generated at the grain boundary and grew toward the inner grain. It was more similar to the morphology of the η- phase, which was analyzed by the EDAX spectra and diffraction patterns as a Cr-rich M23C6 phase instead of the η- phase. The comparison found that after solid solution water cooling + aging and solid solution oil cooling + aging, there are needle-like and massive M23C6 particles and a dotted distribution of MC particles on the grain boundaries. The density of M23C6 particles is larger, and no fine secondary carbides were found on the grain boundaries of the alloys after solid solution furnace cooling + aging and the morphology and size of the primary carbides changed, with the reduction of the short rods and the increase of the lumps, and the size was slightly increased. Figure 10 shows that, due to different cooling methods, the number of M23C6 after heat treatment of the alloy varies greatly, solid solution furnace cooling + aging M23C6 content is relatively more, the mass fraction is as high as 0.037%, the content of MC carbides varies less, basically stabilized at about 0.240%.
2.4 Effect of cooling mode on alloy properties
2.4.1 Cooling mode on the impact properties of the alloy
Figure 11(d) shows the impact absorption energy of the alloy after different solid solution cooling, and the impact properties of the alloy are enhanced with the increase of the cooling rate. The impact properties of the alloy are mainly affected by the grain size change and grain boundary carbides. Fig. 11(a-c) shows the impact fracture SEM images of the alloy, Fig. 11(a, b) shows that the alloy belongs to ductile fracture and Fig. 11(c) shows that the alloy belongs to ductile fracture and deconvoluted fracture. Figure 7(a, b) shows that there are small diffuse carbides on the grain boundaries of the alloy; small and discontinuous carbides on the grain boundaries will prevent the grain boundary slip and greatly enhance the toughness of the alloy, Figure 7(c) there are larger particles of carbides on the grain boundaries of the alloy, and the chain-like distribution, which makes the grain boundaries become a weak zone in the fracture, the grain size of the alloys treated by the three different cooling modes are very similar, the number and size of the carbides on the grain boundaries increase with the decrease of the cooling rate. The number and size of carbides on the grain boundaries increase with the decrease in cooling rate. Therefore, the sharp decrease in impact properties is mainly caused by the increase in the number and size of carbides on the grain boundaries.

Figure.9 TEM image of needle-like carbides in Inconel X-750 alloy after solid solution + water cooling aging treatment
2.4.2 Effect of cooling mode on alloy strength
Figure 12 shows the strength of the alloy after different solid solution cooling + aging; the tensile strength and yield strength of the alloy increase as the cooling rate decreases. The strength of nickel-based high-temperature alloys is mainly determined by the intracrystalline reinforcing phase and the grain boundary reinforcing phase, i.e., the γ’ phase and the grain boundary carbide, the γ’ phase and the M23C6 are face-centered cubic structure, and the matrix co-lattice. The particle size and spacing of the γ’ phase have an important effect on the alloy’s performance; when the size of the γ’ phase is less than 15 nm, the reinforcement mechanism is the dislocations cut across the γ’ phase; when the size of the γ’ phase is greater than 40 nm, the reinforcement mechanism mainly involves the Orowan mechanism. As can be seen in Figure 4, the precipitated strengthening phase in the alloy after solid solution water cooling + aging and solid solution oil cooling + aging is mainly a fine spherical γ’ phase, with a higher number of sizes 5-18 nm and an average size of 15.9 nm, and the dislocations cut through the γ’ particles, thus strengthening the alloy. More cubic and fine spherical γ’ phases precipitated inside the alloy after furnace cooling + aging. The alloy was strengthened by involving the cut-through mechanism and the Orowan mechanism. The mass fraction of γ’ phases was much larger than that of 7.986% for solid solution water cooling + aging and 8.122% for solid solution oil cooling + aging. The density of carbides at the grain boundaries is larger after water and oil cooling, and the presence of carbides with larger particles on the furnace-cooled grain boundaries increases the strength of the alloy with the increase of carbide spacing and carbide size. In summary, the optimum strength of solid solution furnace-cooled + aged alloys depends on the larger γ’ phase mass fraction and the distribution of carbides with larger particles and larger spacing.

Fig.10 SEM images of grain boundary carbides and mass fraction of carbides in Inconel X-750 alloy after solid solution + aging
(a) water cooling + aging; (b) oil cooling + aging; (c) furnace cooling + aging; (d) carbide mass fraction

Fig.11 SEM images of impact fracture and impact absorption energy of Inconel X-750 alloy after solid solution + aging treatment
(a) Water cooling + aging; (b) Oil cooling + aging; (c) Furnace cooling + aging; (d) Impact absorption energy

Fig.12 Strength of Inconel X-750 alloy after different heat treatments

3. Conclusions

• 1) Water cooling and oil cooling inhibit the precipitation of γ’ phase in Inconel X-750 alloy, and a single size spherical γ’ phase is precipitated after aging; cubic and a small amount of spherical γ’ phase is precipitated in the alloy after furnace cooling, and fine spherical γ’ phase is precipitated in the alloy again after aging.
• 2) Inconel X-750 alloy solid solution (water-cooled, oil-cooled) + aging treatment on the grain boundaries of the presence of unmelted MC and precipitation of needle-like M23C6, solid solution (furnace cooling) + aging on the grain boundaries of the presence of unmelted MC and large particles of M23C6.
• 3) Inconel X-750 alloy has the highest strength after solid solution furnace cooling + aging treatment and the best impact properties after solid solution water cooling + aging treatment.

Author: Zhang Yahui