Method for repairing gas turbine blade after wide-temperature-range and long-time thermal exposure damage

Abstract

The invention discloses a method for repairing a gas turbine blade after wide-temperature and long-time thermal exposure damage, and relates to the field of repairing of equiaxial high-temperature alloys for gas turbine blades, a to-be-repaired part is repaired, the to-be-repaired part is a gas turbine blade made of Mar-M247 equiaxial high-temperature alloys, the exposure service time of the to-be-repaired part at 800-1000 DEG C does not exceed 16000 h, and the to-be-repaired part is made of Mar-M247 equiaxial high-temperature alloys. The repairing process comprises the following steps in a vacuum environment: S1, carrying out solution treatment on a to-be-repaired part; s2, high-temperature aging treatment is conducted on the to-be-repaired part subjected to solution treatment; and S3, the to-be-repaired part subjected to high-temperature aging treatment is subjected to low-temperature aging treatment. Solution treatment and secondary aging heat treatment are carried out under the high-vacuum-degree condition, and finally the performance is restored to the level close to or even exceeding the original state level.

Description

Technical Field

[0001] The present invention relates to the field of repairing combustion engine blades with equiaxed high-temperature alloys, and in particular to a method for repairing combustion engine blades damaged by wide-temperature and long-duration heat exposure. Background Art

[0002] The long-term service temperature of gas turbine blades is in the range of 800℃-1000℃, with a total service life of up to 50,000 hours, of which a single overhaul time is as long as 16,000h. Long-term high-temperature thermal exposure will inevitably cause the degradation of the blade material structure and lead to the problem of material performance degradation. The equiaxed nickel-based high-temperature alloys for gas turbines have a high temperature bearing capacity due to the presence of a large number of evenly distributed NiAl3 strengthening phases. They are often used as materials for gas turbine hot-end turbine blades. Among them, the nickel-based high-temperature alloys used for F-class gas turbine blades in service are mostly equiaxed high-temperature alloys. During long-term service, the main strengthening phase of the equiaxed nickel-based high-temperature alloy will appear during long-term thermal exposure. The cubic corners of the phase will be passivated and dissolved, the cubic degree will decrease, the phase will grow coarseningly, and the volume fraction will decrease, which will eventually seriously affect the high-temperature mechanical properties of the alloy and significantly shorten the normal operating life of the engine.

[0003] To effectively restore damaged blade tissue after a gas turbine overhaul cycle and further extend the service life of damaged blades, a suitable restoration heat treatment process is required to repair the damaged microstructure and key mechanical properties of the alloy material. Restoration heat treatment, a heat treatment process that fully or partially restores the microstructure and properties of existing blades, generally includes heat treatment and hot isostatic pressing. Because long-term heat exposure service conditions are similar to no-load conditions, hot isostatic pressing is generally not required; only solution and aging heat treatments are required. Chinese Patent No. 103643188A (published on March 19, 2014) discloses a K465 alloy turbine blade performance restoration heat treatment method. This method restores the long-term performance of K465 alloy turbine blades that have been in service for a short period (500-600 hours). Chinese Patent No. 116423144A (published on July 14, 2023) discloses a restoration process for hot-corrosion-resistant directional alloy turbine blades. This process targets the damage characteristics of long-life directional alloy turbine blades and achieves the restoration of internal metallurgical microstructure damage and typical mechanical properties. Chinese Patent 104878329A (published on September 2, 2015) discloses a heat treatment method for repairing creep damage in directionally solidified DZ125 superalloy turbine blades. This method is suitable for heat treatment of high-temperature, low-stress areas such as the blade airfoil during the middle and late stages of the second creep stage. Chinese Patent 1155884455A (published on January 10, 2023) discloses a heat treatment method for the recovery of nickel-based single crystal superalloys. This method is suitable for second- or third-generation nickel-based single crystal superalloys that have structural damage before the end of the second creep stage.

[0004] In summary, existing patents are mainly aimed at the short-term service damage recovery of oriented crystals and single crystals for gas turbine turbine blades. Therefore, a suitable repair method is needed for Mar-M247 equiaxed high-temperature alloys for gas turbines that have been damaged by high-temperature and long-term thermal exposure. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for repairing gas turbine blades after damage caused by wide-temperature and long-term heat exposure, which is suitable for Mar-M247 equiaxed high-temperature alloy blades that have been exposed to heat at 800-1000°C for no more than 16,000 hours. The method performs solid solution and secondary aging heat treatment under high vacuum conditions, ultimately restoring the performance to a level close to or even exceeding the original level.

[0006] The technical solution adopted by the present invention is as follows: a method for repairing a gas turbine blade damaged by extended-duration thermal exposure at a wide temperature range. The repaired blade is made of a Mar-M247 equiaxed high-temperature alloy and has been exposed to temperatures of 800-1000°C for no more than 16,000 hours. The repair process includes the following steps performed in a vacuum environment: S1: Solution treatment of the repaired parts; S2: subjecting the solution-treated component to be repaired to high-temperature aging treatment; S3: performing low-temperature aging treatment on the repaired parts that have undergone high-temperature aging treatment.

[0007] Furthermore, in step S1, the temperature of the solution treatment is within a heat treatment window that is above the solution temperature of the precipitation strengthening phase and below the initial melting temperature.

[0008] Furthermore, the temperature is raised in two stages during the solution treatment. The first stage of heating is from room temperature to the transition temperature, the transition temperature is 1100℃-1120℃, and the heating rate is not higher than 20℃ / min; the second stage of heating is from the transition temperature to 1180℃-1250℃, and the heating rate is not higher than 15℃ / min and lower than the heating rate of the first stage; after keeping warm for 2-8h, it is cooled to room temperature with argon at a rate close to air cooling.

[0009] Furthermore, in step S2, during the high-temperature aging treatment, the temperature is raised from room temperature to 1000-1150°C at a heating rate not higher than 20°C / min, and the temperature is kept for 2-8 hours. After the temperature is kept, the material is cooled to room temperature by filling with argon at a rate close to air cooling.

[0010] Furthermore, in step S3, during the low-temperature aging treatment, the temperature is raised from room temperature to 800-900°C at a heating rate not higher than 20°C / min, and the temperature is kept for 10-24 hours. After the temperature is kept, the material is cooled to room temperature by filling with argon at a rate close to air cooling.

[0011] Furthermore, before performing step S1, the microstructure of the part to be repaired is subjected to tissue damage standard analysis and mechanical property testing to obtain analysis and test results; based on the analysis and test results, the damage mechanism and distribution characteristics of the part to be repaired are determined, it is determined whether the performance has been significantly degraded, and it is evaluated whether repair is necessary; if repair is necessary, steps S1 to S3 are performed; if repair is not necessary, steps S1 to S3 are not performed.

[0012] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: The method disclosed in the present invention is used to repair the part to be repaired, which is a combustion engine blade made of Mar-M247 equiaxed high-temperature alloy exposed at 800-1000°C for no more than 16000 hours. After the part to be repaired undergoes solution treatment, high-temperature aging treatment and low-temperature aging treatment, the coarse precipitation strengthening phase after damage is The phase is re-dissolved and precipitated into a regular cubic shape with a bimodal particle size distribution of 0.05-0.10μm and 0.38-0.55μm. After the high-temperature long-lasting performance is restored, it exceeds the original state level. The repair method of the present invention has simple and reliable steps and is easy to apply industrially. It has broad prospects in the repair of the matrix structure and performance of domestically produced gas turbine equiaxial high-temperature alloy turbine blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 Strengthen the parts before and after repair Appearance; Figure 2 Performance testing of repaired parts before and after repair Figure 3 The hardness comparison of the repaired part before and after repair. DETAILED DESCRIPTION

[0014] A method for repairing a gas turbine blade after being damaged by a wide temperature and long time heat exposure is used to repair the part to be repaired, which is a gas turbine blade made of Mar-M247 equiaxed high temperature alloy and exposed to 800-1000°C for no more than 16000 hours. Before repairing, the part to be repaired needs to be evaluated, that is, the microstructure of the part to be repaired is subjected to tissue damage standard analysis (including degradation of precipitation-strengthened tissue, degradation of grain boundaries, etc.) and mechanical property testing (including hardness, tensile strength, high temperature endurance, etc.) to obtain analysis and test results; based on the analysis and test results, the part to be repaired is determined. The damage mechanism and distribution characteristics of the parts are determined to determine whether the performance has been significantly reduced and to evaluate whether repair is needed; if repair is needed, steps S1 to S3 are performed; if repair is not needed, steps S1 to S3 are not performed; experiments are conducted on the parts to be repaired, and the repair process includes the following steps under a vacuum environment; the repair environment can be provided by a vacuum furnace, and the parts to be repaired are fixed on a fixture before repair, and after fixing is completed, the parts to be repaired and the fixture are placed in the vacuum furnace together to prevent deformation of the parts to be repaired during the repair process; the subsequent specific steps are as follows.

[0015] S1: Solution treatment is performed on the repaired parts; the temperature of the solution treatment is in the heat treatment window above the solution temperature of the precipitation strengthening phase and below the initial melting temperature. Specifically, the temperature is increased in two stages during the solution treatment. The first stage is from room temperature to the transition temperature, the transition temperature is 1100℃-1120℃, and the heating rate is not higher than 20℃ / min; the second stage is from the transition temperature to 1180℃-1250℃, and the heating rate is not higher than 15℃ / min and lower than the heating rate of the first stage; after keeping warm for 2-8h, cool to room temperature with argon at a rate close to air cooling.

[0016] S2: The repaired parts that have undergone solution treatment are subjected to high-temperature aging treatment under vacuum conditions; during high-temperature aging treatment, the temperature is raised from room temperature to 1000-1150℃ at a heating rate of no more than 20℃ / min, and the temperature is kept for 2-8h. After the temperature is kept, the parts are cooled to room temperature by filling with argon at a rate close to air cooling.

[0017] S3: The repaired part that has undergone high-temperature aging treatment is subjected to low-temperature aging treatment under vacuum conditions; during the low-temperature aging treatment, the temperature is raised from room temperature to 800-900°C at a heating rate of no more than 20°C / min, and the temperature is kept for 10-24 hours. After the temperature is kept, the part is cooled to room temperature by filling with argon at a rate close to air cooling.

[0018] Steps S2 and S3 can effectively promote the growth of the precipitation strengthening phase precipitated after solid solution and adjust its size and uniformity. As shown in Table 2 below, the strengthening phase of the repaired part before and after repair Morphology, size, and distribution.

[0019] Table 2 Strengthening phase of the repaired parts before and after repair Morphology, size, distribution

[0020] The following example is proposed for the specific parameter settings of the repair experiment, as shown in Table 2.

[0021] Table 2 Examples of repair experiments

[0022] The repaired part of Example 2 was compared before and after repair, and the tissue analysis was as follows: Figure 1 As shown, through Figure 1 It can be seen that the tissue of the gas turbine blade is significantly strengthened after damage. Coarsening and merging phenomenon; after solution treatment by this recovery method, the coarse The phase is fully dissolved, and uniform cubic morphology is precipitated from the matrix again after subsequent high and low temperature aging; that is, this repair method can make the coarse strengthening phase after long-term heat exposure damage The re-dissolution results in a regular cubic structure with a bimodal particle size distribution, and its mechanical properties exceed those of the original state. The endurance performance test was carried out at 950℃ and 150MPa. Figure 2 As shown in the figure, it can be seen that the high temperature endurance mechanical properties of the gas turbine blade degraded to 20% of the original after service, and increased to 110% of the original high temperature endurance performance after repair, which is basically consistent with the original. Figure 3 As shown in the figure, the higher the service temperature, the more obvious the hardness decreases after the gas turbine blade is damaged. After repairing with this method, the alloy structure and performance are finally restored. After recovery, the hardness is basically close to that of the body, and the hardness does not change much with the change of service temperature.

[0023] The present invention is not limited to the aforementioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A method for repairing a gas turbine blade after being damaged by long-term heat exposure at a wide temperature range, characterized in that: The repaired part is a gas turbine blade made of Mar-M247 equiaxed high-temperature alloy with an exposure service time of no more than 16,000 hours at 800-1000°C. The repair process includes the following steps in a vacuum environment: S1: Solution treatment of the repaired parts; S2: subjecting the solution treated repaired part to high temperature aging treatment; S3: subjecting the repaired part that has undergone high-temperature aging treatment to low-temperature aging treatment.

2. The repair method according to claim 1, characterized in that: In step S1, the temperature of the solution treatment is within a heat treatment window above the solution temperature of the precipitation strengthening phase and below the initial melting temperature.

3. The repair method according to claim 2, characterized in that: The temperature is raised in two stages during solution treatment. The first stage is from room temperature to transition temperature, the transition temperature is 1100℃-1120℃, and the heating rate is not higher than 20℃ / min; the second stage is from transition temperature to 1180℃-1250℃, the heating rate is not higher than 15℃ / min and is lower than the heating rate of the first stage; after keeping warm for 2-8h, cool to room temperature with argon at a rate close to air cooling.

4. The repair method according to claim 1, characterized in that: In step S2, during the high temperature aging treatment, the temperature is raised from room temperature to 1000-1150°C, the heating rate is not higher than 20°C / min, and the temperature is kept for 2-8 hours. After the temperature is kept, the material is cooled to room temperature by filling with argon at a rate close to air cooling.

5. The repair method according to claim 1, characterized in that: In step S3, during the low-temperature aging treatment, the temperature is raised from room temperature to 800-900°C, the heating rate is not higher than 20°C / min, and the temperature is kept for 10-24 hours. After the temperature is kept, the material is cooled to room temperature by filling with argon at a rate close to air cooling.

6. The repair method according to claim 1, characterized in that: Before performing step S1, a tissue damage standard analysis and a mechanical property test are performed on the microstructure of the repaired part to obtain analysis and test results; According to the analysis and test results, the damage mechanism and distribution characteristics of the part to be repaired are determined, whether the performance is significantly reduced, and whether repair is needed; if repair is needed, steps S1 to S3 are performed; If repair is not required, steps S1 to S3 are not performed.

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