A laser gradient cladding repair method for high-pressure turbine rotor blade hole edge cracks

Abstract

The present application relates to a kind of high-pressure turbine rotor blade hole edge crack laser gradient cladding repair methods, solve the problem of high heat input, low bonding strength, easy to produce micro crack existing in current method.Firstly, the crack area is pretreated, then laser cladding technology is used to fill high-temperature alloy powder containing reinforcing phase layer by layer, and through dynamic thermal field regulation and in-situ stress release process, form good metallurgical bonding with substrate cladding layer, finally, using self-adapting polishing process restores blade profile.The present application avoids the contamination of molten pool in the process of laser cladding by the attachment in the blade inner cavity after service;It is helpful to the powder melting and forming in the process of laser cladding;It is helpful to improve the bonding force of cladding layer;Relieve thermal mismatch stress, at the same time, in-situ post-processing is carried out, which reduces residual stress and helps to improve bonding strength;Using infrared thermometer to monitor the temperature around the molten pool in real time, avoid overheating of the substrate.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine maintenance, and in particular relates to a laser gradient cladding repair method for bore edge cracks in high-pressure turbine rotor blades. Background Technology

[0002] Turbine rotor blades are critical components of aero-engines, operating in harsh environments. The blade tip environment is even more severe than that of the blade body, enduring not only high temperatures and drastic changes in working stress but also susceptibility to corrosion and wear, significantly reducing engine efficiency and blade lifespan. The film cooling holes at the tips of a certain type of high-pressure turbine rotor blade are highly susceptible to cracking and ablation failures under the combined effects of gas backflow, tip effect, and thermal cycling stress. Common repair methods for high-pressure turbine rotor blade tip cracks include argon arc welding, thermal spraying, and laser cladding. Argon arc welding results in high heat input, leading to coarse grains in the heat-affected zone and decreased high-temperature mechanical properties. Thermal spraying has insufficient bonding strength to withstand the dynamic loads of the rotor blade during operation. Conventional laser cladding repair of high-pressure turbine rotor blades suffers from a large coefficient of thermal expansion between the cladding layer and the substrate, making it prone to microcracks. Therefore, it is necessary to research a laser cladding method suitable for high-pressure turbine rotor blade tip cracks. This method can address the challenges of high heat input, low bonding strength, and susceptibility to microcracks, thereby improving the mechanical properties of the repaired area. Summary of the Invention

[0003] This invention provides a laser gradient cladding repair method for bore edge cracks in high-pressure turbine rotor blades, which solves the problems of high heat input, low bonding strength, and easy generation of microcracks in current methods.

[0004] This invention is achieved through the following technical solution: A laser gradient cladding repair method for hole edge cracks in high-pressure turbine rotor blades involves first pre-treating the cracked area, then using laser cladding technology to fill the cracked area layer by layer with high-temperature alloy powder containing reinforcing phases, and forming a cladding layer with good metallurgical bonding with the matrix through dynamic thermal field control and in-situ stress release process. Finally, an adaptive grinding process is used to restore the blade profile.

[0005] Specifically, the following steps are included: S1. Coating removal: Remove the surface coating using chemical or mechanical methods, or a combination of both; S2. Internal cavity cleaning: Clean the inner surface of the blade using methods such as abrasive flow; S3. Beveling: Clean out the cracks around the hole, and then bevele the hole into a funnel shape along the wall thickness direction; S4. Pre-treatment before laser cladding: The bevel surface is treated with pulsed laser to form a micro-textured cross section; S5. Design gradient composite powder: the first layer is 95% NiCrMoNb and 5% YSZ (particle size 50 nm), the second layer is 90% NiCrMoNb and 10% YSZ (particle size 50 nm), and the third layer is 95% NiCrMoNb and 5% YSZ (particle size 50 nm), to achieve cross-distribution of reinforcing phases; S6. Laser Cladding: Laser cladding is used to repair the bevel, with the layer thickness controlled at 0.1~0.2mm. Specific cladding parameters are: annular spot, power: 200~300W, scanning speed: 3~7mm / s, powder feeding rate: 1.5~3.5g / min. At the same time, during the cladding process, the temperature around the molten pool is monitored in real time by an infrared thermometer, and the laser power is dynamically adjusted to ensure that the substrate temperature does not exceed 800℃.

[0006] S7. In-situ post-treatment: Apply high-frequency impact to the repaired area, with a frequency of 10 kHz or higher and an amplitude of 2~10 μm, to reduce the residual stress to below 120 MPa; S8. Profile Restoration: Adaptive machining is used to restore the blade profile to the specified dimensions. S9. Non-destructive testing: Fluorescent flaw detection and X-ray flaw detection.

[0007] The beneficial effects of this invention are: (1) The method of the present invention uses abrasive flow to clean the inner cavity of the blade, which avoids contamination of the molten pool by the adhering material in the inner cavity of the blade after service.

[0008] (2) The method of the present invention is designed with a funnel-shaped bevel, which helps the powder to melt and form during the laser cladding process.

[0009] (3) The method of the present invention uses pulsed laser to treat the bevel surface, forming a micro-textured cross section, which helps to improve the bonding force of the cladding layer.

[0010] (4) The method of the present invention designs a gradient interface to alleviate thermal mismatch stress, and performs in-situ post-treatment to reduce residual stress, which helps to improve the bonding strength.

[0011] (5) The method of the present invention uses an infrared thermometer to monitor the temperature around the molten pool in real time, thus avoiding overheating of the substrate. Attached Figure Description

[0012] Figure 1 A schematic diagram of the bore in a high-pressure turbine rotor blade; Figure 2 A schematic diagram of the bevel of a high-pressure turbine rotor blade; Figure 3 This is a schematic diagram of the laser cladding layer on a high-pressure turbine rotor blade. Detailed Implementation

[0013] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0014] S1. Coating removal: Remove the surface coating using chemical or mechanical methods or a combination of both.

[0015] S2. Internal cavity cleaning: Clean the inner surface of the blade using abrasive flow or other methods.

[0016] S3. Beveling: Clean out any cracks around the hole, then bevele the opening in a funnel shape along the wall thickness direction, such as... Figure 1 , Figure 2 As shown.

[0017] S4. Pretreatment before laser cladding: The bevel surface is treated with pulsed laser to form a micro-textured cross section.

[0018] S5. Design gradient composite powder: The first layer consists of 95% NiCrMoNb and 5% YSZ (particle size 50 nm), the second layer consists of 90% NiCrMoNb and 10% YSZ (particle size 50 nm), and the third layer consists of 95% NiCrMoNb and 5% YSZ (particle size 50 nm), achieving a cross-distribution of reinforcing phases, such as... Figure 3 As shown.

[0019] S6. Laser Cladding: Laser cladding is used to repair the bevel, with the layer thickness controlled at (0.1~0.2) mm. Specific cladding parameters are: annular spot, power: (200~300) W, scanning speed: (3~7) mm / s, powder feeding rate: (1.5~3.5) g / min. Simultaneously, during the cladding process, the temperature around the molten pool is monitored in real time using an infrared thermometer, and the laser power is dynamically adjusted to ensure the substrate temperature does not exceed 800℃.

[0020] S7. In-situ post-treatment: Apply high-frequency impact (frequency above 10 kHz, amplitude 2~10 μm) to the repaired area to reduce residual stress to below 120 MPa.

[0021] S8. Profile restoration: Adaptive machining is used to restore the blade to the specified profile dimensions.

[0022] S9. Non-destructive testing: Fluorescent flaw detection and X-ray flaw detection.

[0023] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A laser gradient cladding repair method for bore edge cracks in high-pressure turbine rotor blades, characterized in that: First, the cracked area is pretreated. Then, high-temperature alloy powder containing reinforcing phases is filled layer by layer using laser cladding technology. Through dynamic thermal field control and in-situ stress release process, a cladding layer with good metallurgical bonding with the matrix is ​​formed. Finally, an adaptive grinding process is used to restore the blade profile. The specific steps include: S1. Coating removal: Remove the surface coating using chemical or mechanical methods, or a combination of both; S2. Internal cavity cleaning: The inner surface of the blade is cleaned using an abrasive flow method; S3. Beveling: Clean out the cracks around the hole, and then bevele the hole into a funnel shape along the wall thickness direction; S4. Pre-treatment before laser cladding: The bevel surface is treated with pulsed laser to form a micro-textured cross section; S5. Design gradient composite powder: the first layer is 95% NiCrMoNb and 5% YSZ, the second layer is 90% NiCrMoNb and 10% YSZ, and the third layer is 95% NiCrMoNb and 5% YSZ, to achieve cross-distribution of reinforcing phases; S6. Laser Cladding: Laser cladding is used to repair the bevel, with the layer thickness controlled between 0.1 and 0.2 mm. At the same time, during the cladding process, the temperature around the molten pool is monitored in real time using an infrared thermometer, and the laser power is dynamically adjusted to ensure that the substrate temperature does not exceed 800 ℃. S7. In-situ post-treatment: Apply high-frequency impact to the repaired area, with a frequency of 10 kHz or higher and an amplitude of 2~10 μm, to reduce the residual stress to below 120 MPa; S8. Profile Restoration: Adaptive grinding process is used to process and repair the blade profile to the specified dimensions; S9. Non-destructive testing.

2. The laser gradient cladding repair method for bore edge cracks of high-pressure turbine rotor blades according to claim 1, characterized in that: In step S5, the particle size of the composite powder is 50 nm.

3. The laser gradient cladding repair method for bore edge cracks of high-pressure turbine rotor blades according to claim 1, characterized in that: step S6 The specific cladding parameters are as follows: annular spot, power: 200~300W, scanning speed: 3~7mm / s, powder feeding rate: 1.5~3.5g / min.

4. The laser gradient cladding repair method for bore edge cracks of high-pressure turbine rotor blades according to claim 1, characterized in that: Non-destructive testing uses fluorescent testing or X-ray testing.

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