Brazing repair method for stop block of stator blade of gas compressor

Abstract

The brazing repair method comprises the following steps that S1, an original wear-resisting piece of the compressor stator blade stop block is removed, S2, a new wear-resisting piece is machined, S3, after purification, the wear-resisting piece and the stator blade stop block are positioned through a spot welding machine, and S4, the wear-resisting piece and the stator blade stop block are subjected to brazing repair. S4, performing a vacuum brazing process in a high-temperature environment of 1160 + / -10 DEG C and a high-vacuum environment of 5 * 10 < 2 > Pa; and S5, two-section type tempering treatment is conducted. According to the technical scheme, the comprehensive performance of the dissimilar material brazed joint is remarkably improved, the strength of the joint is greatly improved, and the high-temperature durability is excellent. And a heat affected zone is strictly controlled, the hardness of a matrix is kept stable, and the dimensional precision and the service reliability are ensured. The maintenance qualified rate is obviously improved, the cost is greatly reduced, and the technical problem of high-quality connection of dissimilar materials in the aviation field is solved.

Description

Technical Field

[0001] This invention relates to the field of compressor stator blade stop blocks; specifically, it relates to a brazing repair method for compressor stator blade stop blocks. Background Technology

[0002] The brazing repair of stator blade stop blocks in aero-engine compressors currently faces several technical challenges. These components, combining martensitic stainless steel and cemented carbide, are prone to wear block detachment or damage under extreme conditions. Traditional repair methods suffer from the following prominent problems: First, poor reliability of the dissimilar material interface. Due to significant differences in physical and chemical properties, a brittle compound layer easily forms during brazing, severely affecting the joint's mechanical properties. This brittle phase is more likely to become a crack initiation point under high temperature and pressure, leading to early failure. Second, difficulty in controlling the heat-affected zone (HAZ). The thermal cycling during brazing adversely affects the base material, potentially causing microstructural changes and performance degradation. For martensitic stainless steel, this may result in over-tempering or microstructural coarsening; for cemented carbide, the high-temperature process may cause oxidation of the binder phase or compositional changes. Third, difficulty in ensuring dimensional accuracy. Aero-engine components require extremely high dimensional accuracy, but thermal deformation and shrinkage during brazing often lead to dimensional deviations, affecting assembly accuracy and performance. This is particularly challenging for blade components with complex profiles, where maintaining shape is especially difficult. Fourth, maintaining consistent quality presents significant challenges. Existing repair processes lack stability, resulting in substantial fluctuations in quality between different batches. The lack of effective non-destructive testing methods to accurately assess repair quality makes it difficult to ensure that every repaired part meets stringent aviation standards. Furthermore, the economic viability of repair processes needs improvement. Traditional methods require complex procedures and expensive specialized equipment, leading to high repair costs. Simultaneously, the long repair cycles fail to meet the demands for rapid maintenance in aviation operations. Summary of the Invention

[0003] The purpose of this invention is to provide a brazing repair method for the stop block of the compressor stator blade in order to solve the problems existing in the prior art described in the background.

[0004] The technical solution adopted by this invention to solve its technical problem is: a brazing repair method for the stop block of a compressor stator blade, comprising the following steps: S1: Remove the original wear-resistant material from the compressor stator blade stop block and polish the machined surface to a surface roughness ≤ Ra1.6μm; S2: Process new wear-resistant sheets, and use a grinding machine to grind the weld surface of the brazed joints to achieve a surface roughness ≤ Ra 1.6μm. The new wear-resistant sheets should be suitable for use at 1180℃±5℃ and a vacuum degree ≤ 1×10⁻⁶. -2Keep warm under Pa conditions for 20-25 minutes to thoroughly remove surface oxides; S3: After purification, the wear-resistant sheet is positioned by spot welding with the stator blade stop block. The wear-resistant sheet's dimensions exceed the stop block by 0-0.2mm. Amorphous brazing foil strip Niflex 76 is used to fix it to the wear-resistant sheet's welding joint by spot welding. S4: Brazing, which includes two stages: First stage: The first stage involves isothermal solidification of the brazing filler metal at 1160℃, with a controlled heating rate of 10℃ / min and a holding time of 10min. Second stage: The section is cooled to 900℃ at a slow cooling rate of 10℃ / min and then subjected to temperature homogenization treatment; S5: Tempering process, including two stages: First stage: Medium-temperature tempering at 600~620℃ for 2 hours; Second stage: High-temperature tempering at 610~630℃ for 2 hours; S5: Inspect the repaired compressor stator blade stop block.

[0005] Preferred option: In S1, after the blade is fixed with a special tooling, it is installed in a five-axis linkage precision machining center to perform surface treatment on the compressor stator blade stop block to remove the original wear-resistant sheet.

[0006] Preferred: In S2, the new wear-resistant plate is made of YG15 cemented carbide and is formed by grinding and cutting with a diamond wheel, with a size of 9.5mm*3mm*1.3mm.

[0007] Preferably, in S3, the spot welding parameters are set to current 8-12A, pressure 40±3N, and duration 0.3-0.6s, and the copper rod used for spot welding has a diameter greater than half the length of the wear-resistant plate; Preferred: In S4, brazing is performed at 5×10⁻ 2 The experiment was conducted under a high vacuum environment.

[0008] Compared with the prior art, the present invention has the following beneficial effects: The technical solution of this invention significantly improves the overall performance of brazed joints made of dissimilar materials, resulting in a substantial increase in joint strength and excellent high-temperature durability. The heat-affected zone is strictly controlled, and the matrix hardness remains stable, ensuring dimensional accuracy and service reliability. The repair qualification rate is significantly improved while costs are substantially reduced, solving the technical challenge of high-quality joining of dissimilar materials in the aerospace field. Detailed Implementation

[0009] This invention discloses a brazing repair method for a compressor stator blade stop block. First, the compressor stator blade is fixed with a special tooling and then installed in a five-axis linkage precision machining center. The surface of the stop block is treated to remove the original wear-resistant pad, and the machined surface is polished to a surface roughness ≤ Ra 1.6μm. For YG15 cemented carbide, it is precision ground and cut with a diamond wheel to form a size of 9.5mm*3mm*1.3mm. The weld surface of the brazed joint is machined with a grinding machine to a surface roughness ≤ Ra 1.6μm.

[0010] After processing, the new wear-resistant pads undergo surface treatment and high-temperature vacuum purification, followed by high-vacuum heat treatment in a high-vacuum heat treatment furnace (ultimate vacuum ≤5×). Optimization treatment is carried out in the following process: YG15 cemented carbide is subjected to 1180℃±5℃ and vacuum degree≤1× Under the specified conditions, maintain the temperature for 20-25 minutes to thoroughly remove surface oxides. After cleaning, the wear-resistant sheet is precisely positioned to the stator blade stop block using a spot welding machine. The parameters are set as follows: current 8-12A, pressure 40±3N, duration 0.3-0.6s. The copper rod used for spot welding has a diameter greater than half the length of the wear-resistant sheet. The wear-resistant sheet must ensure assembly accuracy, with its circumference exceeding the stop block by 0-0.2mm. Amorphous brazing foil Niflex 76 (10mm×2mm strip) is used and fixed to the welded joint of the wear-resistant sheet by spot welding.

[0011] Vacuum brazing process at a high temperature of 1160℃±10℃ and 5×10 ⁻2 The process was conducted under a high vacuum environment (Pa) and employed an innovative two-stage precision temperature control strategy: In the first stage, the solder was isothermally solidified at 1160℃, with a precise heating rate of 10℃ / min and a holding time of 10min to ensure thorough wetting and metallurgical bonding of the solder; in the second stage, a slow cooling rate of 10℃ / min was used to reduce the temperature to 900℃, followed by isothermal homogenization to promote uniform element diffusion and reduce structural stress. This segmented temperature control method not only ensured sufficient flow and diffusion of the solder but also effectively prevented overheating damage and grain growth in the matrix material, significantly improving the bonding quality and reliability of the interface.

[0012] A two-stage tempering process was innovatively designed for post-weld microstructure control and stress relief: the first stage employs a medium-temperature tempering process at 600-620℃ for 2 hours, effectively eliminating over 80% of residual welding stress and improving the material's toughness and stability; the second stage involves a high-temperature tempering process at 610-630℃ for 2 hours, further promoting carbide dispersion and microstructure homogenization, significantly enhancing the material's high-temperature performance and fatigue resistance. Both stages utilize air cooling, ensuring stress relief while avoiding quenching stress, achieving synergistic optimization of microstructure and residual stress, and solving the technical challenge of traditional single-stage tempering in simultaneously achieving stress relief and microstructure stability.

[0013] Specialized testing methods include mechanical property testing and non-destructive testing. Mechanical testing involves applying 1100N of pressure to the wear-resistant area using a specially designed fixture for 5 seconds to verify the joint's crack resistance. Non-destructive testing employs fluorescent penetrant testing, strictly adhering to the HB / Z 61-2018 Class B standard, to reliably detect micron-level surface defects. The combined use of these two methods allows for a comprehensive assessment of the joint's quality and reliability.

[0014] This patent develops a brazing repair method for dissimilar materials in aero-engine stop blocks. Through a high-temperature vacuum purification process at 1170℃ and a specialized brazing filler metal, the thickness of the brittle interfacial layer is controlled to within 2μm. A novel two-stage gradient brazing and two-stage tempering process reduces the width of the heat-affected zone to 0.25mm. A combined mechanical and non-destructive testing system is established, ensuring an 80% factory pass rate. This technology increases the room temperature shear strength to 120MPa, a 50% improvement over traditional methods, and systematically solves the challenges of interface control, microstructure optimization, and quality assessment in dissimilar material bonding.

[0015] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A brazing repair method for a compressor stator blade stop block, characterized in that, Includes the following steps: S1: Remove the original wear-resistant pads from the compressor stator blade stop block and polish the machined surface to a surface roughness ≤ Ra 1.6μm; S2: Process new wear-resistant sheets, and use a grinding machine to grind the weld surface of the brazed joints to achieve a surface roughness ≤ Ra 1.6μm. The new wear-resistant sheets should be suitable for use at 1180℃±5℃ and a vacuum degree ≤ 1×10⁻⁶. -2 Keep warm under Pa conditions for 20-25 minutes to thoroughly remove surface oxides; S3: After purification, the wear-resistant sheet is positioned by spot welding with the stator blade stop block. The wear-resistant sheet's dimensions exceed the stop block by 0-0.2mm. Amorphous brazing foil Niflex 76 is used to fix it to the wear-resistant sheet's welding joint by spot welding. S4: Brazing, which includes two stages: First stage: The first stage involves isothermal solidification of the brazing filler metal at 1160℃, with a controlled heating rate of 10℃ / min and a holding time of 10min. Second stage: The section is cooled to 900℃ at a slow cooling rate of 10℃ / min and then subjected to temperature homogenization treatment; S5: Tempering process, including two stages: First stage: Medium-temperature tempering at 600~620℃ for 2 hours; Second stage: High-temperature tempering by holding at 610~630℃ for 2 hours; S5: Inspect the repaired compressor stator blade stop block.

2. The brazing repair method for a compressor stator blade stop block according to claim 1, characterized in that: In S1, after the blades are fixed with special tooling, they are installed in a five-axis linkage precision machining center to perform surface treatment on the compressor stator blade stop block to remove the original wear-resistant material.

3. The brazing repair method for a compressor stator blade stop block according to claim 1, characterized in that: In S2, the new wear-resistant pad is made of YG15 cemented carbide and is formed by grinding and cutting with a diamond wheel. The size is 9.5mm*3mm*1.3mm.

4. The brazing repair method for a compressor stator blade stop block according to claim 1, characterized in that: In S3, the spot welding parameters are set to current 8-12A, pressure 40±3N, and duration 0.3-0.6s. The copper rod used for spot welding has a diameter greater than half the length of the wear-resistant plate.

5. The brazing repair method for a compressor stator blade stop block according to claim 1, characterized in that: In S4, brazing is performed at 5×10 -2 The experiment was conducted under a high vacuum environment.