CN121006501A

CN121006501A - A heat treatment method for high-temperature alloys and powder high-temperature alloys

Info

Publication number: CN121006501A
Application number: CN202511219085.7A
Authority: CN
Inventors: 程俊义; 刘朝峰; 马向东; 肖磊; 郭建政; 冯干江
Original assignee: Shenzhen Wedge Zhongnan Research Institute Co ltd
Current assignee: Shenzhen Wedge Zhongnan Research Institute Co ltd
Priority date: 2025-08-28
Filing date: 2025-08-28
Publication date: 2025-11-25

Abstract

The invention discloses a heat treatment method of a high-temperature alloy and a powder high-temperature alloy, and relates to the technical field of high-temperature alloy preparation. The heat treatment method comprises the steps of S1, preserving the temperature of the powder high-temperature alloy at a solid solution treatment temperature T _sol for 0-8 hours, S2, cooling the alloy to (T _γ'-30℃)～(T_γ' -150) at a cooling rate of 30-80 ℃ per minute, S3, cooling the alloy to room temperature at a cooling rate of 100-600 ℃ per minute, and S4, preserving the temperature for 4-24 hours at 760-815 ℃ and cooling to room temperature. The invention effectively and cooperatively improves the strength and the plasticity of the powder high-temperature alloy at high temperature, realizes the optimal configuration of different parts of the turbine disc at high temperature (such as 800 ℃) tensile property, gives consideration to the overall strength and the local plasticity, breaks through the contradiction between strength and plasticity in the traditional heat treatment on the premise of not greatly changing components and not remarkably increasing the cost, and provides a low-cost and high-performance regulation and control way for manufacturing high-end equipment.

Description

Heat treatment method of high-temperature alloy and powder high-temperature alloy

Technical Field

The invention relates to the technical field of high-temperature alloy preparation, in particular to a heat treatment method of a high-temperature alloy and a powder high-temperature alloy.

Background

The application of the powder metallurgy technology in the field of turbine disc preparation effectively solves the problem of macrosegregation caused by the traditional casting and forging technology, and provides an important guarantee for the tissue uniformity of the high-performance nickel-based superalloy. With the continuous rise of the working temperature of aeroengines and gas turbines, more severe requirements are put on turbine disks to maintain high strength and high plasticity at the same time in a high-temperature environment. At present, by solid solution treatment and a continuous cooling process combined with high cooling rate, fine gamma' phases distributed in a dispersed manner can be formed in the alloy, so that remarkable strength improvement is realized. However, this process tends to result in a significant drop in plasticity, limiting the reliability of its application in extreme environments, subject to the strength-plasticity inversion relationships common in metallic materials.

The inverse relationship between strength and plasticity described above is essentially due to the lack of ability of the material to harden during deformation. When the work hardening rate cannot match the increase in rheological stress, strain localization and early necking are easily induced, resulting in plastic instability. Therefore, the key to increasing the high temperature plasticity of superalloys is to enhance their uniform deformability and work hardening rate. The current research shows that the dislocation can be promoted to be uniformly wound, proliferated and stored in the deformation by the methods of phase change induced plasticity, twin induced plasticity, grain refinement regulation and control, principal component optimization, precipitated phase morphology design and the like, and the method is an effective way for improving the plasticity.

Further from the alloy component system, typical third generation powder superalloys (such as FGH4113A, FGH, FGH99, ME3 and LSHR) have similar phase transformation mechanisms and strengthening mechanisms, although the contents of the main strengthening elements such as Al, co, cr, mo, W, ti, nb, ta are relatively close, which indicates that the plasticization strategy has universality in a certain range. However, current methods for achieving strength-plasticity co-promotion still rely mainly on adjusting the principal components of the alloy or optimizing the hot working process, which not only significantly increases the development cycle and manufacturing costs, but also increases the process complexity.

In particular, in the heat treatment stage, the conventional process focuses on controlling the size and distribution of the γ' phase by rapid continuous cooling to strengthen the alloy, but it is difficult to avoid the contradiction between strength-plasticity. Therefore, how to develop a new heat treatment method capable of cooperatively improving the strength and plasticity of the powder superalloy by breaking through the prior performance bottleneck through technological innovation without greatly increasing the cost is a core technical problem to be solved in the current field.

Disclosure of Invention

The invention aims to solve the technical problem that the high-temperature strength and the plasticity are difficult to be simultaneously achieved in the traditional heat treatment method of the high-temperature alloy.

In order to solve the problems, the invention provides the following technical scheme:

the invention provides a heat treatment method of a high-temperature alloy, which comprises the following steps:

s1, preserving heat of the powder high-temperature alloy for 0-8 hours at a solution treatment temperature T _sol;

S2, cooling the alloy to (T _γ'-30℃)～(T_γ' -150 ℃) at a cooling rate of 30-80 ℃ per minute, wherein T _γ' is the complete solid solution temperature of gamma' -phase of the powder high-temperature alloy;

s3, cooling the powder high-temperature alloy to room temperature at a cooling rate of 100-600 ℃ per minute;

And S4, preserving the temperature of the powder superalloy for 4-24 hours at 760-815 ℃, and cooling to room temperature.

Further, the technical scheme is that T _sol is (T _γ'-15℃)～(T_γ' +50 ℃).

Further, the technical scheme is that T _sol is (T _γ)～(T_γ' +30 ℃).

In the further technical scheme, in the step S2, the alloy is cooled to (T _γ'-50℃)～(T_γ' -70 ℃) at a cooling rate of 30-80 ℃ per minute.

According to the technical scheme, the room-temperature molar ratio of the gamma' phase in the powder superalloy is 45-60%.

In the further technical scheme, in the step S1, after solution treatment, the grain size in the alloy is increased to 6.5-9.5 levels.

The technical scheme is that after the heat treatment method is adopted, the equivalent diameter of the large-size gamma ' phase in the finally obtained alloy is 1-5 mu m, the equivalent diameter of the medium-size gamma ' phase is 100-300 nm, and the equivalent diameter of the small-size gamma ' phase is 10-70 nm.

The heat treatment method is suitable for treating the powder superalloy containing 16-21.5wt% of Co, 12-14wt% of Cr, 6-8wt% of Al+Ti, 2-6wt% of 2-Nb+Ta, 8-12wt% of 2-Mo+W and the balance of grain boundary strengthening elements C, B, hf, zr.

The invention also provides a preparation method of the powder superalloy, which comprises the heat treatment method of the superalloy.

The invention also provides a powder superalloy, which is prepared by the preparation method of the powder superalloy, wherein the equivalent diameter of a large-size gamma ' phase is 1-5 mu m, the equivalent diameter of a medium-size gamma ' phase is 100-300 nm, and the equivalent diameter of a small-size gamma ' phase is 10-70 nm.

Compared with the prior art, the invention has the following technical effects:

According to the heat treatment method of the high-temperature alloy, provided by the invention, the strength and plasticity of the powder high-temperature alloy at high temperature are effectively and cooperatively improved through a multi-stage precise temperature control heat treatment process. According to the invention, firstly, heat preservation is carried out at the near-solid solution temperature or the over-solid solution temperature, so that crystal grains are moderately coarsened, the total proportion of crystal boundaries is reduced, thereby obviously inhibiting a deformation mechanism leading by crystal boundary sliding and diffusion creep at high temperature, and improving the creep resistance and high-temperature stability of the material. In the cooling stage after solid solution, the invention adopts a sectional cooling strategy, wherein the first stage is cooled to a preset temperature below the solid solution temperature of the gamma ' phase at a slow speed, so that the gamma ' phase of the first batch slowly precipitates and properly grows, and then the second stage is subjected to rapid cooling, and the gamma ' phase of the second batch with small and uniform size is supplemented in a gamma channel. The accurate cooling control process effectively controls the precipitation behavior and distribution form of the gamma' phase, reduces the cracking risk of the disc caused by instantaneous high thermal stress, and improves the reliability and the yield of the treatment process.

The invention can also realize the optimal configuration of different parts of the turbine disc at high temperature (such as 800 ℃) tensile property, and has the advantages of overall strength and local plasticity, and breaks through the contradiction between strength and plasticity in the traditional heat treatment on the premise of not greatly changing components and not obviously increasing cost, thereby providing a low-cost and high-performance regulation and control way for manufacturing high-end equipment.

According to the heat treatment method of the high-temperature alloy, disclosed by the invention, the multi-scale gamma' -precipitation phase coexisting microstructure can be successfully constructed in the third-generation powder high-temperature alloy turbine disc by introducing a multi-stage precise temperature control heat treatment process. The method effectively coordinates the strengthening and toughening effects of the gamma' phase precipitated in different sizes, thereby obviously improving the plasticity while improving the high-temperature strength, and successfully solving the contradiction that the high-temperature strength and the plasticity are difficult to be compatible in the traditional heat treatment process.

The heat treatment method of the high-temperature alloy provided by the invention is essentially to realize the cooperative promotion of strength-plasticity by accurately regulating and controlling the size and the distribution of gamma 'phase in the alloy, is universally applicable to all third-generation powder high-temperature alloys taking gamma' phase as main strengthening phase, and has wide engineering applicability and popularization value.

Drawings

FIG. 1 is a graph showing the differential thermal analysis cooling profile of DTA for powder superalloy FGH4113A used in the examples and comparative examples of the present invention.

FIG. 2 is a graph of the gamma prime phase ratio versus temperature for FGH4113A alloy calculated by the phase diagram calculation method (CALPHAD).

FIG. 3 is a metallographic photograph of the FGH4113A alloy used in the examples and comparative examples of the present invention as-forged.

FIG. 4 is an inverse pole diagram of the as-forged EBSD of FGH4113A alloy used in the examples and comparative examples of the present invention.

FIG. 5 is a photograph of electrolytic corrosion of example 2.

FIG. 6 is a photograph of electrolytic corrosion of example 3.

FIG. 7 is a photograph of electrolytic corrosion of example 6.

FIG. 8 is a photograph of electrolytic corrosion of comparative example 1.

Fig. 9 is the average size of the secondary and tertiary gamma prime phases after solution treatment of the comparative and partial examples calculated using thermodynamic software package Pandat.

Fig. 10 is the secondary, tertiary and aged gamma prime phase volume fractions after the complete heat treatment for the comparative and partial examples calculated using thermodynamic software package Pandat.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments. It will be apparent that the embodiments described below are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be understood that the terms "comprises" and "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It is also to be understood that the terminology used in the description of the embodiments of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of embodiments of the invention. As used in the specification of the embodiments of the invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The embodiment of the invention provides a heat treatment method of a high-temperature alloy, aiming at the problem that the high-temperature strength and plasticity of a powder high-temperature alloy turbine disc subjected to hot isostatic pressing, hot extrusion and isothermal forging are difficult to be compatible, comprising the following steps of:

S1, preserving the temperature of the powder high-temperature alloy for 0-8 hours at a solution treatment temperature T _sol.

Through solution treatment, the large-size gamma ' phase generated in the powder superalloy manufacturing process (hot isostatic pressing, hot extrusion and isothermal forging process) is reduced or completely melted, so that the pinning of gamma ' relative to a grain boundary is reduced, and the large-size gamma ' phase is prevented from being left after heat treatment. Meanwhile, through solution treatment, crystal grains can be moderately coarsened, the overall proportion of crystal boundaries is reduced, so that a deformation mechanism which is dominant by grain boundary sliding and diffusion creep at high temperature is restrained, and the creep resistance and high-temperature stability of the material are improved. Thus, the solution treatment temperature T _sol is near or greater than the complete solution temperature T _γ' of the powder superalloy gamma prime phase.

In a specific implementation, the complete solid solution temperature T _γ' of the powder superalloy γ' phase is measured using differential thermal method (DTA), differential Scanning Calorimetry (DSC), phase diagram calculation method (calhad) or metallographic method.

In the specific implementation, the grain size in the powder superalloy is increased to 6.5-9.5 grade, preferably 7.5-8.5 grade, by solution treatment.

In one embodiment, the solution treatment temperature T _sol is (T _γ'-15℃)～(T_γ' +50 ℃) and does not exceed (T _γ' +50 ℃) to avoid abnormal grain growth. Preferably T _sol is (T _γ)～(T_γ' +30℃).

S2, cooling the powder superalloy to (T _γ'-30℃)～(T_γ' -150 ℃) at a cooling rate of 30-80 ℃ per minute.

The alloy is cooled to a specific temperature below the complete solid solution temperature T _γ', for example (T _γ'-30℃～(T_γ' -150 ℃), preferably (T _γ'-50℃)～(T_γ' -70 ℃) by adopting a conventional air furnace or vacuum quenching furnace and cooling methods such as air cooling, vacuum air cooling and the like at a cooling rate of 30-80 ℃ per minute, so that the first gamma '-phase slowly precipitates and grows properly (called secondary gamma').

S3, cooling the powder superalloy to room temperature at a cooling rate of 100-600 ℃ per minute.

And (3) by adjusting parameters such as inflation pressure or fan rotation speed, the cooling rate is increased to 100-600 ℃ per minute, and a second gamma 'phase (called tertiary gamma') with small size and uniform distribution is supplemented in the gamma channel. Preferably, the cooling speed is 250-350 ℃ per minute.

The specific temperature in step S2 is measured by a welding thermocouple. In some embodiments, according to the simulation calculation, the specific temperature is indirectly controlled by controlling the cooling duration (cooling rate) in the step S2, so as to optimize the different size distributions of the gamma' phase by combining slow cooling and fast cooling.

It will be appreciated that powder superalloys, such as nickel-base superalloys for disks, whose gamma prime precipitation kinetics determine that the precipitation is batch, and therefore, under conventional continuous cooling processes, batch precipitation is also characteristic. In the invention, the first stage is cooled slowly and has higher temperature, the precipitated secondary gamma 'phase has larger size, and the second stage is cooled quickly and has high temperature falling speed, and the precipitated tertiary gamma' phase has smaller size.

This stage, also called ageing treatment, can be carried out in a conventional air furnace or vacuum gas quenching furnace, and cooling can be carried out by furnace cooling, air cooling or oil cooling. The aging treatment can consume oversolidated solubility in the matrix and supplement aging gamma 'phases (called aging gamma') which are small in size and uniformly distributed. Preferably, the aging treatment system is kept at 760 ℃ for 16 hours or at 815 ℃ for 8 hours.

The heat treatment method of the high-temperature alloy provided by the invention is essentially to realize the cooperative promotion of strength and plasticity by precisely regulating and controlling the size and the distribution of the gamma 'phase in the alloy, so that the heat treatment method of the invention is universally applicable to all third-generation powder high-temperature alloys taking the gamma' phase as a main strengthening phase. Powder superalloys as shown in table 1 below.

Table 1 powder superalloy composition (wt.%)

	Al	Co	Cr	Mo	Nb	Ti	W	Ta	Ni	2*Al+Ti	2*Nb+Ta	2*Mo+W
													FGH4113A	3.0	19.0	13.0	4.0	1.2	3.7	4.0	1.0	Bal.	9.7	3.4	12
FGH98	3.5	20.4	12.7	3.8	0.9	3.7	2.1	2.4	Bal.	10.7	4.2	9.7
													FGH99	3.6	20.0	13.0	2.9	1.5	3.5	4.3	1.5	Bal.	10.7	4.5	10.1
ME3	3.4	20.6	13.0	3.8	0.9	3.7	2.1	2.4	Bal.	10.5	4.2	9.7
													LSHR	3.5	21.0	13.0	2.7	1.5	3.5	4.3	1.6	Bal.	10.5	4.6	9.7

In order to clearly demonstrate the practical effect of the present invention, the following examples and comparative examples all use a third generation powder superalloy FGH4113A subjected to the same hot forming and hot deformation processes, the initial average grain size is 8-9 grade, and the metallographic photograph in the as-forged state and the EBSD inverse polar diagram are shown in fig. 3 and 4.

The differential thermal analysis cooling curve of the extruded alloy DTA of FGH4113A is shown in FIG. 1, and the ratio of gamma prime phase to temperature in the FGH4113A alloy calculated by the phase diagram calculation method (CALPHAD) is shown in FIG. 2.

Example 1

The embodiment provides a heat treatment method for a superalloy, which improves the strength and plasticity of a FGH4113A powder superalloy turbine disc by heat treatment. The method comprises the following specific steps:

(1) Using a conventional heat treatment furnace, the temperature is raised to 1175+ -10 ℃ at a temperature rise rate of not higher than 10 ℃ per minute, and the heat is preserved for 2.5 hours.

(2) The alloy was cooled to 1065.+ -. 10 ℃ at a cooling rate of about 44 ℃/min.

(3) The alloy was cooled to room temperature at a cooling rate of about 459 ℃/min.

(4) And (3) aging heat treatment, namely preserving heat for 8 hours at the temperature of 815 ℃ and air cooling.

Example 2

(2) The alloy was cooled to 1020.+ -. 10 ℃ at a cooling rate of about 75 ℃ per minute.

(3) The alloy was cooled to room temperature at a cooling rate of about 594 ℃ per minute.

Example 3

(2) The alloy was cooled to 1100.+ -. 10 ℃ at a cooling rate of about 65 ℃ per minute.

(3) The alloy was cooled to room temperature at a cooling rate of about 295C/min.

Example 4

(2) The alloy was cooled to 1090.+ -. 10 ℃ at a cooling rate of about 50 ℃/min.

(3) The alloy was cooled to room temperature at a cooling rate of about 197 ℃ per minute.

Example 5

(2) The alloy was cooled to 1090.+ -. 10 ℃ at a cooling rate of about 61 ℃/min.

(3) The alloy was cooled to room temperature at a cooling rate of about 181 ℃ per minute.

Example 6

(2) The alloy was cooled to 1090.+ -. 5 ℃ at a cooling rate of about 51 ℃/min.

(3) The alloy was cooled to room temperature at a cooling rate of about 121 ℃ per minute.

Comparative example 1

(2) The alloy was cooled to room temperature at a cooling rate of about 150 ℃ per minute.

(3) And (3) aging heat treatment, namely preserving heat for 8 hours at the temperature of 815 ℃ and air cooling.

The alloys FGH4113A after heat treatment of examples 1-6 and comparative example 1 were subjected to the relevant performance test at 800℃and the results are shown in Table 2. The electrolytic corrosion photographs of examples 2, 3 and 6 are respectively shown in fig. 5 to 7, the electrolytic corrosion photograph of comparative example 1 is shown in fig. 8, and the corresponding average size results of gamma 'phase and volume fraction of gamma' phase under different treatment processes are shown in fig. 9 and 10.

It can be seen that the comparative example has a smaller total amount of precipitation of the tertiary gamma ' phase and the aged gamma ' phase, indicating that such conventional cooling treatment cannot flexibly adjust the size distribution of the gamma ' phase. While the secondary gamma' phase size of the embodiment is affected by the cooling rate of the first section, and increases with the cooling rate, the volume fraction of the embodiment is affected by the specific turning temperature, and increases with the lowering of the turning temperature. In addition, the small size of the examples (including tertiary gamma ' and aged gamma ') has a higher gamma ' phase content, the ratio of tertiary gamma ' phase increases with a specific turn temperature rise, and the size of tertiary gamma ' phase decreases with the second stage cooling rate increase. Obviously, by controlling the cooling rate, the size distribution of the gamma' phase in the turbine disc can be effectively adjusted.

TABLE 2 alloy Properties after Heat treatment for examples 1-6 and comparative example 1

Table 2 the results show that all examples have significantly improved plasticity index while maintaining high strength compared to comparative example 1, which uses a conventional continuous cooling process (about 150C/min). Wherein, examples 1 to 4 effectively regulate the size distribution and volume fraction of the γ' phase by adjusting the first stage cooling rate (about 50-75 ℃ per minute), the specific cooling temperature (1020-1090 ℃) and the second stage cooling rate (121-594 ℃) so as to optimize the performance matching. With the increase of the cooling rate of the second stage, the tensile strength of the alloy is slightly reduced to 924MPa from the highest 987MPa, the maximum reduction is only 6.4%, the elongation after fracture is greatly increased to 27% from the lowest 14.5%, and the maximum increase reaches 107.7%. The change trend shows that the process can obviously improve the high-temperature plasticity of the material on the premise of less strength loss.

As can be seen from fig. 9 and 10, the heat treatment method of the superalloy provided by the invention can effectively regulate and control the precipitation behavior and size distribution of gamma' phase, and is helpful for improving dislocation storage capacity and work hardening rate, so as to cooperatively enhance the high temperature strength and plasticity of the material.

The heat treatment method of the high-temperature alloy has good controllability and stability, can realize the collaborative design of the strength and the plasticity of the high-temperature alloy by optimizing the gamma' -phase structure, solves the problem that the two are difficult to be compatible in the traditional process, and has important engineering application value.

In the foregoing embodiments, the descriptions of the embodiments are focused on, and for those portions of one embodiment that are not described in detail, reference may be made to the related descriptions of other embodiments.

While the invention has been described with reference to certain preferred embodiments, it will be understood by those skilled in the art that various changes and substitutions of equivalents may be made and equivalents will be apparent to those skilled in the art without departing from the scope of the invention. Therefore, the protection scope of the invention is subject to the protection scope of the claims.

Claims

1. A heat treatment method for a high-temperature alloy, characterized by comprising the following steps:

S1. Hold the powdered high-temperature alloy at a solution treatment temperature _Tsol for 0 to 8 hours.

S2. Cool the alloy to (T _γ' -30℃) to (T _γ' -150℃) at a cooling rate of 30 to 80℃/min, where T _γ' is the complete solution temperature of the γ' phase of the powder superalloy.

S3. Cool the powder superalloy to room temperature at a cooling rate of 100-600℃/min;

S4. Hold the powdered high-temperature alloy at 760-815℃ for 4-24 hours, then cool it to room temperature.

2. The heat treatment method for high-temperature alloys as described in claim 1, characterized in that _Tsol is (Tγ _' -15℃) to (Tγ _' +50℃).

3. The heat treatment method for high-temperature alloys as described in claim 2, characterized in that _Tsol is ( _Tγ ) to (Tγ _' + 30℃).

4. The heat treatment method for high-temperature alloys as described in claim 1, characterized in that, in step S2, the alloy is cooled to (T _γ' -50℃) to (T _γ' -70℃) at a cooling rate of 30 to 80℃/min.

5. The heat treatment method for high-temperature alloys as described in claim 1, wherein the room temperature molar percentage of the γ' phase in the powder high-temperature alloy is 45-60%.

6. The heat treatment method for high-temperature alloys as described in claim 1, characterized in that, in step S1, after solution treatment, the grain size in the alloy increases to level 6.5 to 9.5.

7. The heat treatment method for high-temperature alloys as described in claim 1, characterized in that, after the heat treatment method, the final alloy has an equivalent diameter of 1-5 μm for the large-size γ' phase, an equivalent diameter of 100-300 nm for the medium-size γ' phase, and an equivalent diameter of 10-70 nm for the small-size γ' phase.

8. The heat treatment method for high-temperature alloys as described in claim 1, characterized in that the heat treatment method is applicable to treating powder high-temperature alloys containing the following elements: Co 16-21.5 wt.%, Cr 12-14 wt.%, Al+Ti 6-8 wt.%, 2*Nb+Ta 2-6 wt.%, 2*Mo+W 8-12 wt.%, and the remainder being grain boundary strengthening elements: C, B, Hf, Zr.

9. A method for preparing a powder superalloy, characterized in that it includes the heat treatment method for the superalloy as described in any one of claims 1-8.

10. A powder superalloy, characterized in that it is prepared by the preparation method of claim 9, wherein the equivalent diameter of the large-size γ' phase is 1-5 μm; the equivalent diameter of the medium-size γ' phase is 100-300 nm; and the equivalent diameter of the small-size γ' phase is 10-70 nm.