Brazing method for DD26 single-crystal high-temperature alloy and MX62 wear-resistant alloy

Abstract

The invention relates to the technical field of single-crystal high-temperature alloy welding, in particular to a brazing method for DD26 single-crystal high-temperature alloy and MX62 wear-resistant alloy. The method specifically comprises the following four steps: step 1, brazing treatment; step 2, primary aging heat treatment; step 3, gas phase aluminizing; and 4, coating diffusion and secondary aging co-treatment. Brazing treatment (1180 DEG C), primary aging heat treatment (1080 DEG C), gas-phase aluminizing (950 DEG C) and coating diffusion and secondary aging co-treatment (870 DEG C) are carried out, and the temperature of the heat treatment process is reduced from high to low. According to a blade structure obtained after welding, the gamma'phase keeps the original cubic shape and is small in size, dendritic crystal trunk and dendritic crystal gamma 'phase are small in size difference and free of raft formation, meanwhile, recrystallization does not occur on the surface of a blade body, a strengthening phase in MX62 abrasion-resistant alloy does not decompose, the tensile strength of a welded joint at the temperature of 950 DEG C reaches 361 MPa, the shear strength at the temperature of 950 DEG C reaches 326 MPa, and the endurance life of the welded joint at the temperature of 950 DEG C / 75 MPa reaches 96 h.

Description

Technical Field

[0001] The invention relates to the technical field of single crystal high temperature alloy welding, in particular to a brazing method for a DD26 single crystal high temperature alloy and an MX62 wear-resistant alloy. Background Art

[0002] DD26 is a nickel-based precipitation hardening single crystal high temperature alloy with a service temperature below 1100℃. The alloy has high creep strength and fatigue resistance, and has good structural stability. After long-term aging at 900℃ for 2000h, no harmful TCP phase is precipitated. It also has good casting performance, welding performance and coating performance. DD26 single crystal high temperature alloy is mainly used to make aircraft engine gas turbine rotor blades and guide vanes.

[0003] For high-pressure turbine discs and single-crystal high-pressure turbine blades with double-tenon root structure design, the blade crown mating surface will induce resonance under centrifugal force and aerodynamic excitation force, resulting in high-temperature micro-motion wear. The high-temperature micro-motion wear resistance of DD26 single-crystal high-temperature alloy is insufficient. In order to improve the high-temperature micro-motion wear resistance of the blade crown position, it is necessary to braze high-temperature wear-resistant alloy on the blade crown mating surface. At the same time, in order to improve the oxidation resistance and corrosion resistance of the single-crystal blade flow surface organization, it is necessary to apply special functional coatings. The residual stress introduced during the coating pretreatment process becomes the driving force for blade recrystallization. When the brazing temperature exceeds 1200℃, the alloy will undergo rapid recrystallization and organization rafting, resulting in a decrease in fatigue performance. At the same time, it will also cause the strengthening phase in the MX62 wear-resistant alloy to decompose, resulting in a decrease in the wear performance of the alloy.

[0004] Therefore, it is necessary to develop a brazing method suitable for DD26 single crystal high-temperature alloy and MX62 wear-resistant alloy, which can reduce the rafting and recrystallization of the single crystal structure while avoiding the decomposition of the strengthening phase in the wear-resistant alloy, so as to improve the service life of the single crystal high-pressure turbine working blades. Summary of the invention

[0005] In order to solve the above technical problems existing in the prior art, the present invention provides a brazing method for DD26 single crystal high temperature alloy and MX62 wear-resistant alloy, which is specifically achieved through the following technical scheme.

[0006] A brazing method for DD26 single crystal high temperature alloy and MX62 wear-resistant alloy comprises the following steps:

[0007] Step 1: Brazing

[0008] First, the DD26 single crystal high-pressure turbine blades were solution treated, and the MX62 wear-resistant block and the blade crown mating surface were spot welded and positioned, and then the N300E brazing material was filled in the weld position, and then placed in a vacuum heat treatment furnace for high-temperature brazing. The temperature was first raised to 500°C, then raised to 1050°C and kept warm, and then continued to rise to 1180°C and kept warm. Then, when the furnace was cooled to 1100°C, argon gas was filled for rapid cooling.

[0009] Step 2: Primary aging heat treatment

[0010] The brazed single crystal high-pressure turbine blades are placed in a heat treatment furnace for heat treatment at 1080°C, and then heat-insulated and air-cooled.

[0011] Step 3: Vapor Aluminization

[0012] The single crystal high-pressure turbine blade after the primary aging is placed in a heat treatment furnace, and vapor phase aluminizing is performed at 950°C for aluminizing time, and air cooling;

[0013] Step 4: Coating diffusion and secondary aging co-treatment

[0014] The single crystal high-pressure turbine blades that have completed vapor phase aluminum infiltration are placed in a heat treatment furnace and heat treated at 870°C. After being heated through, they are kept warm and air-cooled to complete the co-treatment of coating diffusion and secondary aging.

[0015] Furthermore, in the step 1, the temperature is first raised to 500° C., specifically, the temperature is raised to 500° C. at a rate of 4° C. / min to 8° C. / min.

[0016] Furthermore, in the step 1, the temperature is raised to 1050° C. and then kept warm, specifically, the temperature is raised to 1050° C. at 8° C. to 15° C. and then kept warm for 30 min to 40 min.

[0017] Furthermore, in the step 1, the temperature is continued to be raised to 1180° C. and then kept warm, specifically, the temperature is continued to be raised at 8° C. to 15° C. and then kept warm for 15 min to 20 min.

[0018] Furthermore, the rapid cooling is performed by filling with argon gas, specifically filling with 2 bar to 3 bar of argon gas.

[0019] Furthermore, in step 2, the insulation time is 2 hours.

[0020] Furthermore, in step three, the aluminizing time is 4h-5h.

[0021] Furthermore, in step 4, the insulation time is 24 hours.

[0022] Furthermore, the air cooling is cooling under room temperature air.

[0023] Compared with the prior art, the technical effects created by the present invention are embodied in:

[0024] (1) The brazing method of the present invention has a simple process, can be mass-produced, does not change the conditions of the factory's heat treatment equipment, has a low process cost, and has a significant effect;

[0025] (2) The brazing method of the present invention can avoid the rafting of the single crystal structure and the decomposition of the wear-resistant alloy strengthening phase, and at the same time can reduce the occurrence of recrystallization on the blade surface.

[0026] (3) The brazing method of the present invention can realize the brazing connection between DD26 single crystal and MX62 wear-resistant alloy. The blade microstructure after brazing by the brazing method of the present application maintains the original cubic shape of the γ' phase and is small in size. The size difference between the dendrite trunk and the dendrite γ' phase is small, and rafting does not occur. At the same time, no recrystallization occurs on the blade surface, and the strengthening phase in the MX62 wear-resistant alloy does not decompose. The tensile strength of the brazed joint at 950°C reaches 361MPa, the shear strength at 950°C reaches 326MPa, and the endurance life at 950°C / 75MPa reaches 96h. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The brazing temperature variation curve of the DD26 single crystal high temperature alloy blade and the MX62 wear-resistant alloy in Embodiment 1 of the present invention;

[0028] Figure 2 The microstructure of the DD26 single crystal superalloy blade in the solid solution aging state without brazing process;

[0029] Figure 3 This is a microstructure photograph of the DD26 single crystal high temperature alloy blade after brazing in Example 1 of the present invention;

[0030] Figure 4 This is a microstructure photo of the comparative example DD26 single crystal high temperature alloy blade after brazing;

[0031] Figure 5 This is a microstructure photo of MX62 wear-resistant alloy that has not undergone the brazing process;

[0032] Figure 6 This is a microstructure photograph of the MX62 wear-resistant alloy after brazing in Example 1 of the present invention;

[0033] Figure 7 This is a microstructure photograph of the comparative example MX62 wear-resistant alloy after brazing;. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further defined below in conjunction with specific implementation methods, but the scope of protection required is not limited to the description.

[0035] Embodiment 1:

[0036] The brazing process of the present invention is divided into four steps. Step 1 is brazing treatment: after spot welding the MX62 wear-resistant block and the blade crown mating surface, fill the weld position with N300E brazing material and place it in a vacuum heat treatment furnace for high-temperature brazing. First, heat it to 500°C at 4°C to 8°C, then heat it to 1050°C at 8°C to 15°C and keep it warm for 30min to 40min, continue to heat it to 1180°C at 8°C to 15°C and keep it warm for 15min to 20min, then cool it to 1100°C with the furnace, and fill it with 2bar to 3bar argon for rapid cooling. Step 2 is an aging heat treatment: put the single crystal high-pressure turbine blade after brazing into a heat treatment furnace, heat treat it at 1080°C, keep it warm for 2h after heating through, and air cool it. Step 3 is vapor aluminizing: put the single crystal high-pressure turbine blade after the primary aging into a heat treatment furnace, vapor aluminize at 950°C for 4h-5h, and air cool. Step 4 is coating diffusion and secondary aging co-treatment: put the single crystal high-pressure turbine blade after the vapor aluminizing into a heat treatment furnace, heat treat at 870°C, heat-insulate for 24h after heat penetration, air cool, and complete the coating diffusion and secondary aging co-treatment.

[0037] The same process was used to braze the furnace samples. After brazing, the mechanical properties and microstructure of the brazed samples were tested.

[0038] Comparative Example 1:

[0039] The brazing process of the present invention is divided into three steps. Step one is brazing treatment: first, the DD26 single crystal high-pressure turbine blade is subjected to solid solution + primary aging treatment, the B-Ni55 brazing material is filled in the weld position, and the blade is placed in a vacuum heat treatment furnace for high-temperature brazing. First, the temperature is raised to 550°C at 5°C to 15°C, then the temperature is raised to 1150°C at 7°C to 15°C and then kept warm for 30min to 40min, and then the temperature is raised to 1225°C at 7°C to 15°C and then kept warm for 20min to 40min, and then when the furnace is cooled to 1100°C, 1bar to 2bar argon is filled for rapid cooling. Step two is vapor phase aluminizing: the single crystal high-pressure turbine blade after the primary aging is placed in a heat treatment furnace, vapor phase aluminizing is performed at 950°C, the aluminizing time is 4h-5h, and air cooling is performed. Step three is coating diffusion treatment: put the single crystal high-pressure turbine blade that has completed vapor phase aluminum infiltration into a heat treatment furnace, perform heat treatment at 850°C, keep the heat for 24 hours after heating through, and air cool to complete the coating diffusion treatment. The same process is used to braze the furnace samples. After brazing, the mechanical properties and microstructure analysis of the brazed samples are performed.

[0040] Table 1 shows the mechanical property test results of the brazing joints of DD26 single crystal high temperature alloy and MX62 wear-resistant alloy in Example 1 and the comparative example and the statistical value of the MX62 strengthening phase content.

[0041] Table 1 Mechanical properties of brazed joints of Example 1 and comparative example and content of MX62 strengthening phase

[0042]

[0043] The brazing temperature variation curve of the DD26 single crystal high temperature alloy blade and the MX62 wear-resistant alloy in Example 1 is shown in Figure 1 .from Figure 1 It can be seen that the method of the present application clarifies the heating rate, holding time and argon filling rapid cooling requirements when brazing DD26 single crystal high temperature alloy and MX62 wear-resistant alloy.

[0044] The raw materials that have not undergone the brazing process (solution-aged DD26 single crystal high-temperature alloy blades that have not undergone the brazing process, and MX62 wear-resistant alloy that has not undergone the brazing process) are compared with the structures obtained after brazing in Example 1 and Comparative Example 1. The specific results are shown in Figure 2-7 .

[0045] from Figure 2 It can be seen that the γ' phase in the microstructure of the solution-aged DD26 single crystal superalloy blade that has not undergone the brazing process presents a good cubic shape and a small size, and there is only a small difference in the size of the dendrite trunk and dendrite γ' phase.

[0046] from Figure 3 It can be seen that the cubic degree of the γ' phase of the microstructure of the DD26 single crystal high-temperature alloy blade after brazing in Example 1 of the present invention is still maintained at a good level, the size difference between the dendrite trunk and the dendrite γ' phase is not large, and the structure is not rafted.

[0047] from Figure 4 It can be seen that the size of the γ' phase in the microstructure of the comparative DD26 single crystal high-temperature alloy blade after brazing is significantly increased, the degree of cubicization is significantly deteriorated, and the structure shows an obvious rafting trend.

[0048] from Figure 5 It can be seen that the NbC strengthening phase in the microstructure of the MX62 wear-resistant alloy that has not undergone the brazing process has clear boundaries and rounded contours, and the NbC phase accounts for 17.45%.

[0049] from Figure 6 It can be seen that in the microstructure of the MX62 wear-resistant alloy after brazing in Example 1 of the present invention, the NbC strengthening phase has a clear boundary and a rounded contour, wherein the NbC phase accounts for 18.32%.

[0050] from Figure 7 It can be seen that in the microstructure of the comparative example MX62 wear-resistant alloy after brazing, the boundary of the NbC strengthening phase is clear, the outline has not changed, but the content has decreased, and the proportion of NbC phase is 13.29%.

[0051] It can be seen from the above that the brazing method in the embodiment can effectively avoid the decomposition of the strengthening phase in the wear-resistant alloy. At the same time, since the single crystal structure is not rafted, the high-temperature tensile strength, high-temperature shear strength and high-temperature endurance performance of the alloy are better than those of the comparative example.

[0052] Finally, it should be pointed out that the above embodiments are only representative examples of the present invention. Obviously, the technical solution of the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by ordinary technicians in this field should be considered as the protection scope of the present invention.

Claims

1. A brazing method for DD26 single crystal high temperature alloy and MX62 wear-resistant alloy, characterized in that: The following steps are involved: Step 1: Brazing First, the DD26 single crystal high-pressure turbine blades were solution treated, and the MX62 wear-resistant block and the blade crown mating surface were spot welded and positioned, and then the N300E brazing material was filled in the weld position, and then placed in a vacuum heat treatment furnace for high-temperature brazing. The temperature was first raised to 500°C, then raised to 1050°C and kept warm, and then continued to rise to 1180°C and kept warm. Then, when the furnace was cooled to 1100°C, argon gas was filled for rapid cooling. Step 2: Primary aging heat treatment The brazed single crystal high-pressure turbine blades are placed in a heat treatment furnace for heat treatment at 1080°C, and then heat-insulated and air-cooled. Step 3: Vapor Aluminization The single crystal high-pressure turbine blade after the primary aging is placed in a heat treatment furnace, and vapor phase aluminizing is performed at 950°C for aluminizing time, and air cooling; Step 4: Coating diffusion and secondary aging co-treatment The single crystal high-pressure turbine blades that have completed vapor phase aluminum infiltration are placed in a heat treatment furnace and heat treated at 870°C. After being heated through, they are kept warm and air-cooled to complete the co-treatment of coating diffusion and secondary aging.

2. The brazing method of DD26 single crystal high temperature alloy and MX62 wear-resistant alloy according to claim 1, characterized in that: In the step 1, the temperature is first raised to 500° C., specifically, the temperature is raised to 500° C. at 4° C. / min to 8° C. / min.

3. The brazing method of DD26 single crystal high temperature alloy and MX62 wear-resistant alloy according to claim 1, characterized in that: In the step 1, the temperature is raised to 1050° C. and then kept warm, specifically, the temperature is raised to 1050° C. at 8° C. to 15° C. and then kept warm for 30 min to 40 min.

4. The brazing method of DD26 single crystal high temperature alloy and MX62 wear-resistant alloy according to claim 1, characterized in that: In the step 1, the temperature is continuously raised to 1180° C. and then kept warm. Specifically, the temperature is continuously raised at 8° C. to 15° C. and then kept warm for 15 min to 20 min.

5. The brazing method of DD26 single crystal high temperature alloy and MX62 wear-resistant alloy according to claim 1, characterized in that: The rapid cooling is carried out by filling with argon gas, specifically filling with 2 bar to 3 bar of argon gas.

6. The brazing method of DD26 single crystal high temperature alloy and MX62 wear-resistant alloy according to claim 1, characterized in that: In the step 2, the insulation time is 2 hours.

7. The brazing method of DD26 single crystal high temperature alloy and MX62 wear-resistant alloy according to claim 1, characterized in that: In the step 3, the aluminizing time is 4h-5h.

8. The brazing method of DD26 single crystal high temperature alloy and MX62 wear-resistant alloy according to claim 1, characterized in that: In the step 4, the insulation time is 24 hours.

9. The brazing method of DD26 single crystal high temperature alloy and MX62 wear-resistant alloy according to claim 1, characterized in that: The air cooling is cooling under room temperature air.

Images