Thermal deformation heat treatment method for improving grain boundary characteristic distribution of deformed high-temperature alloy

Abstract

The invention belongs to the technical field of deformation high-temperature alloy forming machining, and discloses a thermal deformation heat treatment method for improving grain boundary characteristic distribution of deformation high-temperature alloy. The method comprises the following steps: placing the wrought superalloy in a heat treatment furnace, heating the heat treatment furnace to a primary heat preservation temperature, and carrying out primary heat preservation treatment on the wrought superalloy in the furnace; the heat treatment furnace continues to be heated to the secondary heat preservation temperature, and secondary heat preservation treatment is conducted on the deformed high-temperature alloy in the furnace; carrying out compression deformation treatment on the deformed high-temperature alloy subjected to the secondary heat preservation treatment to obtain a compression deformation high-temperature alloy; and the compression deformation high-temperature alloy is subjected to solid solution heat treatment and air cooling. According to the method, the proportion of low-energy special grain boundaries in the wrought superalloy can be increased, and the durability of the wrought superalloy is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of deformed high-temperature alloy forming and processing, and more specifically, relates to a hot deformation heat treatment method for improving the distribution of grain boundary characteristics of deformed high-temperature alloy. Background Art

[0002] The high-temperature resistance of superalloys is a key indicator for their application in fields such as aerospace, energy, and chemical engineering. However, grain boundaries, as the weak link in superalloys, are often the primary source of failure and fracture under high temperature and stress. Specifically, grain boundaries are prone to stress concentration, element segregation, and void nucleation, leading to crack initiation and propagation. Therefore, reducing the number of grain boundaries or optimizing the grain boundary type / orientation has become an important approach to improving the mechanical properties and high-temperature stability of deformed superalloys.

[0003] At the same time, long-term durability is a key performance indicator for high-temperature alloys in extreme service environments. For high-temperature alloys used in critical applications such as aeroengine hot-end components, gas turbine blades, and nuclear reactor cores, their value lies not only in their short-term high-temperature strength but also in their ability to resist slow deformation (creep) and ultimately fracture under the combined effects of long-term high temperatures and stresses. However, under the long-term effects of high temperatures and high stresses, grain boundaries often become the weakest link in material failure. This is primarily due to the irregular atomic arrangement at grain boundaries, which makes them a favorable location for vacancies to nucleate and grow during creep, leading to the initiation and propagation of wedge-shaped cracks along the grain boundaries. Furthermore, harmful elements tend to segregate at grain boundaries, reducing their bonding strength and potentially promoting the precipitation of harmful brittle phases, further accelerating the failure process. Therefore, achieving excellent long-term durability requires not only superior strength and toughness in the matrix itself, but also alloying design and advanced fabrication techniques to suppress grain boundary weakening, hinder grain boundary sliding, and slow intergranular crack propagation.

[0004] Different types of grain boundaries in high-temperature alloys exhibit significant differences in their properties. Conventional high-angle grain boundaries (randomly oriented) tend to be preferential pathways for crack initiation and propagation under high-temperature stress, serving as primary sites for creep void nucleation. Low-Σ coincidence position lattice grain boundaries (CSL boundaries, particularly Σ3 twin boundaries) exhibit lower grain boundary energy and higher structural stability, effectively suppressing damage accumulation through grain boundary sliding and diffusion control.

[0005] At present, the grain boundary control methods for deformed high-temperature alloys mainly focus on controlling the grain size, such as refining or coarsening the grains through thermomechanical processing (such as hot rolling, hot extrusion) or heat treatment processes (such as solution treatment, aging treatment). However, these grain boundary control methods have limited effect on controlling the proportion of special grain boundaries (such as low Σ coincidence position lattice grain boundaries, i.e., CSL grain boundaries). Previous studies have pointed out that a high proportion of special grain boundaries (such as Σ3 twin boundaries) can significantly improve the creep resistance and oxidation resistance of the alloy, but the existing control methods are relatively simple and can only be achieved through a small amount of cold deformation combined with subsequent heat treatment. However, this method not only has a narrow process window (mainly manifested in high precision requirements for cold deformation and low fault tolerance), but is also difficult to effectively combine with the actual hot forming process of high-temperature alloy components (such as hot extrusion, hot rolling and subsequent heat treatment), which limits its industrial application. Therefore, it is urgent to develop a process method that can achieve the following goals at the same time:

[0006] Goal 1: Significantly increase the proportion of special grain boundaries; Goal 2: Seamlessly connect with existing hot forming processes; Goal 3: Increase the durability of deformed high-temperature alloys by more than 30%. Summary of the Invention

[0007] The present invention addresses the shortcomings of existing technologies and proposes a method for heat treatment of deformed superalloys to improve the distribution of grain boundary characteristics. The method of the present invention can increase the proportion of low-energy special grain boundaries in the deformed superalloys, effectively improving the durability of the deformed superalloys.

[0008] In order to achieve the above object, the present invention provides a hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy, the method comprising the following steps:

[0009] S1: placing the deformed high-temperature alloy in a heat treatment furnace, heating the heat treatment furnace to a primary holding temperature, and performing a primary holding treatment on the deformed high-temperature alloy in the furnace;

[0010] S2: continuing to heat the heat treatment furnace to a secondary holding temperature, and performing a secondary holding treatment on the deformed high-temperature alloy in the furnace;

[0011] S3: performing compression deformation treatment on the deformed high-temperature alloy after the secondary heat preservation treatment to obtain a compression-deformed high-temperature alloy;

[0012] S4: performing solution heat treatment on the compression-deformed high-temperature alloy and air cooling.

[0013] The mechanism of action of the thermal deformation + heat treatment of the present invention is: a certain amount of residual deformation and dislocation substructure are introduced into the deformed alloy through appropriate thermal deformation. During the subsequent solution heat treatment process, the random grain boundaries of the alloy migrate and react with the dislocation substructure in the deformed structure, inducing annealing twin nucleation, thereby increasing the proportion of low-energy special grain boundaries in the alloy.

[0014] According to the present invention, preferably, the deformed high-temperature alloy in step S1 is obtained by vacuum melting and casting.

[0015] In the present invention, the deformed superalloy in step S1 is a deformed superalloy suitable for hot-formed components. According to the present invention, preferably, the deformed superalloy in step S1 is a high-strength and tough nickel-cobalt-chromium based deformed superalloy and / or a high-strength and tough iron-nickel-chromium based deformed superalloy.

[0016] According to the present invention, preferably, the nickel-cobalt-chromium based deformable high-temperature alloy is IN617 alloy.

[0017] According to the present invention, preferably, the iron-nickel-chromium based deformable high-temperature alloy is GH1059 alloy.

[0018] According to the present invention, preferably, based on the total weight of the GH1059 alloy, the chemical composition of the GH1059 alloy includes: C: 0.04-0.09%, Mn: 1.2-1.8%, Cr: 14-17%, Ni: 35-37%, Mo: 3-3.5%, B: 0.001-0.002%, Nb: 0.1-0.5%, Zr: 0-0.02%, Y: 0-0.02%, N: 0-0.02%, O≤0.01%, Pb≤0.001%, Bi≤0.0001%, As≤0.005%, Sb≤0.01%, Sn≤0.005%, Al≤0.1%, Co≤0.1%, Si≤0.2%, Cu≤0.1%, P≤0.015%, S≤0.01%, and the balance is Fe.

[0019] In the present invention, the heat treatment furnace is a resistance heat treatment furnace.

[0020] According to the present invention, preferably, in step S1:

[0021] The heating rate is 10-20℃ / min;

[0022] The primary heat preservation temperature is 1100-1120° C.; and the primary heat preservation treatment time is 0.5-2 hours.

[0023] According to the present invention, preferably, in step S2:

[0024] The heating rate is 10-20℃ / min;

[0025] The secondary insulation temperature is 1150-1200° C.; and the secondary insulation treatment time is 2-6 hours.

[0026] According to the present invention, preferably, in step S3:

[0027] The temperature of the compression deformation treatment is the end temperature of the secondary heat preservation treatment, and the strain rate of the compression deformation treatment is 10 -4 ~1s -1 The deformation amount of the compression deformation treatment is controlled at 10% to 80%.

[0028] According to the present invention, preferably, in step S4:

[0029] The temperature of the solution heat treatment is 1000-1150° C., and the time is 0.5-20 hours.

[0030] In the present invention, "air cooling" means cooling the compression-deformed high-temperature alloy to room temperature through air after solution heat treatment.

[0031] The beneficial effects of the technical solution of the present invention are as follows:

[0032] The thermal deformation heat treatment method of the present invention is suitable for the manufacture of key high-temperature structural components of thermal forming, and can increase the proportion of low-energy special grain boundaries in deformed high-temperature alloys.

[0033] The thermal deformation heat treatment method of the present invention has the characteristics of simple process, controllable parameters and strong industrial applicability.

[0034] The thermal deformation heat treatment method of the present invention is based on a conventional hot forming process system. By precisely controlling the key process parameters of alloy hot forming and subsequent heat treatment, the dynamic recrystallization process and grain boundary migration behavior are effectively controlled during the solution treatment process, thereby promoting the nucleation and growth of annealing twins and optimizing their interaction mechanism, ultimately achieving the technical effect of significantly improving the proportion of low-energy special grain boundaries.

[0035] The method of the present invention is a hot deformation + heat treatment method for improving the durability of deformed high-temperature alloys by precisely controlling the grain boundary types. By optimizing the distribution of grain boundary characteristics, namely grain boundary engineering, the proportion of total low-energy special grain boundaries in the deformed high-temperature alloy is increased to more than 75%, effectively improving the durability of the deformed high-temperature alloy (the durability life of the deformed high-temperature alloy is increased by more than 30%), and has great application potential.

[0036] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0037] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Instead, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0038] Example 1

[0039] This embodiment provides a hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy. The target deformed high-temperature alloy to be improved is GH1059 alloy.

[0040] Based on the total weight of the GH1059 alloy, the chemical composition of the GH1059 alloy includes: C: 0.05%, Mn: 1.70%, Cr: 15.50%, Ni: 35.90%, Mo: 3.35%, B: 0.0012%, Nb: 0.24%, Zr: 0.01%, Y: 0.0025%, N: 0.011%, impurity elements O≤0.01%, Pb≤0.001%, Bi≤0.0001%, As≤0.005%, Sb≤0.01%, Sn≤0.005%, Al≤0.1%, Co≤0.1%, Si≤0.2%, Cu≤0.1%, P≤0.015%, S≤0.01%, and the balance is Fe.

[0041] The method comprises the following steps:

[0042] S1: placing the GH1059 alloy in a resistance heat treatment furnace, heating the resistance heat treatment furnace to 1110° C. at a rate of 15° C. / min, and performing a holding treatment on the deformed high-temperature alloy in the furnace at 1110° C. for 1 hour;

[0043] S2: the heat treatment furnace is further heated up to 1180° C. at a rate of 15° C. / min, and the deformed high-temperature alloy in the furnace is subjected to a secondary holding treatment at 1180° C. for 4 hours;

[0044] S3: at 1180℃ and strain rate 10 -2 s -1 Under the condition of 100 ℃, the deformed high-temperature alloy after the secondary heat preservation treatment is subjected to compression deformation treatment to obtain a compression-deformed high-temperature alloy with a deformation amount of 30%;

[0045] S4: performing solution heat treatment on the compression-deformed high-temperature alloy at 1080° C. for 15 hours, and air-cooling to room temperature to obtain an improved GH1059 alloy.

[0046] Example 2

[0047] This embodiment provides a hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy. The target deformed high-temperature alloy to be improved is GH1059 alloy, which is the same as that in Example 1.

[0048] The method comprises the following steps:

[0049] S1: placing the GH1059 alloy in a resistance heat treatment furnace, heating the resistance heat treatment furnace to 1100° C. at a rate of 15° C. / min, and performing a holding treatment on the deformed high-temperature alloy in the furnace at 1100° C. for 0.5 hour;

[0050] S2: the heat treatment furnace is further heated up to 1150° C. at a rate of 15° C. / min, and the deformed high-temperature alloy in the furnace is subjected to a secondary holding treatment at 1150° C. for 2 hours;

[0051] S3: at 1150℃ and strain rate 10 -4 s -1 Under the condition of 10%, the deformed high-temperature alloy after the secondary heat preservation treatment is subjected to compression deformation treatment to obtain a compression-deformed high-temperature alloy with a deformation amount of 10%;

[0052] S4: performing solution heat treatment on the compression-deformed high-temperature alloy at 1000° C. for 20 hours, and air-cooling to room temperature to obtain an improved GH1059 alloy.

[0053] Example 3

[0054] This embodiment provides a hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy. The target deformed high-temperature alloy to be improved is GH1059 alloy, which is the same as that in Example 1.

[0055] The method comprises the following steps:

[0056] S1: placing the GH1059 alloy in a resistance heat treatment furnace, heating the resistance heat treatment furnace to 1120° C. at a rate of 15° C. / min, and performing a holding treatment on the deformed high-temperature alloy in the furnace at 1120° C. for 2 hours;

[0057] S2: The heat treatment furnace is further heated up to 1200° C. at a rate of 15° C. / min, and the deformed high-temperature alloy in the furnace is subjected to a secondary heat preservation treatment at 1200° C. for 6 hours;

[0058] S3: at 1200°C and strain rate 1s -1 Under the condition of , the deformed high temperature alloy after the secondary heat preservation treatment is subjected to compression deformation treatment to obtain a compression deformed high temperature alloy with a deformation amount of 50%;

[0059] S4: performing solution heat treatment on the compression-deformed high-temperature alloy at 1150° C. for 0.5 hour, and air-cooling to room temperature to obtain an improved GH1059 alloy.

[0060] Example 4

[0061] This embodiment provides a hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy. The target deformed high-temperature alloy to be improved is GH1059 alloy, which is the same as that in Example 1.

[0062] The method comprises the following steps:

[0063] S1: placing the GH1059 alloy in a resistance heat treatment furnace, heating the resistance heat treatment furnace to 1100° C. at a rate of 15° C. / min, and performing a holding treatment on the deformed high-temperature alloy in the furnace at 1100° C. for 0.5 hour;

[0064] S2: the heat treatment furnace is further heated up to 1150° C. at a rate of 15° C. / min, and the deformed high-temperature alloy in the furnace is subjected to a secondary holding treatment at 1150° C. for 2 hours;

[0065] S3: at 1150℃ and strain rate 10 -2 s -1 Under the condition of 100 ℃, the deformed high-temperature alloy after the secondary heat preservation treatment is subjected to compression deformation treatment to obtain a compression-deformed high-temperature alloy with a deformation amount of 20%;

[0066] S4: performing solution heat treatment on the compression-deformed high-temperature alloy at 1050° C. for 20 hours, and air-cooling to room temperature to obtain an improved GH1059 alloy.

[0067] Comparative Example 1

[0068] This comparative example provides a method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy. The target deformed high-temperature alloy to be improved is the same as that in Example 1.

[0069] The comparative example method includes the following steps: forging and hot rolling the GH1059 alloy at 1150° C., and then solutionizing it at 1120° C. for 0.5 h to obtain the improved GH1059 alloy.

[0070] Test Case

[0071] The ratio of Σ3 twin boundaries, the ratio of Σ9+Σ27 grain boundaries, and the ratio of total low-energy special grain boundaries (Σ3 to Σ29) in the improved GH1059 alloy of the embodiment and the comparative example were obtained by EBSD (electron backscatter diffraction) analysis.

[0072] The improved GH1059 alloys of the examples and comparative examples were placed under conditions of 750° C. and 135 MPa to obtain the endurance test results of the improved GH1059 alloys of the examples and comparative examples.

[0073] The results are shown in Table 1.

[0074] Table 1

[0075]

[0076] From Table 1 we can see that:

[0077] After being treated by the thermal deformation heat treatment method provided by the present invention, the special grain boundary ratio of the deformed high-temperature alloy is greatly increased, and the durability of the alloy is effectively improved, with the durability life generally increased by more than 27%.

[0078] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy, characterized in that: The method comprises the following steps: S1: placing the deformed high-temperature alloy in a heat treatment furnace, heating the heat treatment furnace to a primary holding temperature, and performing a primary holding treatment on the deformed high-temperature alloy in the furnace; S2: continuing to heat the heat treatment furnace to a secondary holding temperature, and performing a secondary holding treatment on the deformed high-temperature alloy in the furnace; S3: performing compression deformation treatment on the deformed high-temperature alloy after the secondary heat preservation treatment to obtain a compression-deformed high-temperature alloy; S4: performing solution heat treatment on the compression-deformed high-temperature alloy and air cooling.

2. The hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy according to claim 1, wherein: The deformed high-temperature alloy in step S1 is obtained by vacuum melting and casting.

3. The hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy according to claim 2, wherein: The deformed high-temperature alloy in step S1 is a nickel-cobalt-chromium based deformed high-temperature alloy and / or an iron-nickel-chromium based deformed high-temperature alloy.

4. The hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy according to claim 3, wherein: The nickel-cobalt-chromium based deformable high-temperature alloy is IN617 alloy.

5. The hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy according to claim 3, wherein: The iron-nickel-chromium based deformable high-temperature alloy is GH1059 alloy.

6. The hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy according to claim 5, wherein: Based on the total weight of the GH1059 alloy, the chemical composition of the GH1059 alloy includes: C: 0.04-0.09%, Mn: 1.2-1.8%, Cr: 14-17%, Ni: 35-37%, Mo: 3-3.5%, B: 0.001-0.002%, Nb: 0.1-0.5%, Zr: 0-0.02%, Y: 0-0.02%, N: 0-0.02%, O≤0.01%, Pb≤0.001%, Bi≤0.0001%, As≤0.005%, Sb≤0.01%, Sn≤0.005%, Al≤0.1%, Co≤0.1%, Si≤0.2%, Cu≤0.1%, P≤0.015%, S≤0.01%, and the balance is Fe.

7. The hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy according to claim 1, wherein: In step S1: The heating rate is 10-20℃ / min; The primary heat preservation temperature is 1100-1120° C.; and the primary heat preservation treatment time is 0.5-2 hours.

8. The hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy according to claim 1, wherein: In step S2: The heating rate is 10-20℃ / min; The secondary insulation temperature is 1150-1200° C.; and the secondary insulation treatment time is 2-6 hours.

9. The hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy according to claim 1, wherein: In step S3: The temperature of the compression deformation treatment is the end temperature of the secondary heat preservation treatment, and the strain rate of the compression deformation treatment is 10 -4 ~1s -1 The deformation amount of the compression deformation treatment is controlled at 10% to 80%.

10. The hot deformation heat treatment method for improving the distribution of grain boundary characteristics of a deformed high-temperature alloy according to claim 1, wherein: In step S4: The temperature of the solution heat treatment is 1000-1150° C., and the time is 0.5-20 hours.

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