A method for repairing refractory metal parts based on supersonic laser deposition technology

Abstract

A refractory metal part repairing method based on supersonic laser deposition technology, steps: the surface of the refractory metal part to be repaired is subjected to oil removal and roughening treatment; the refractory metal powder with same composition is selected and subjected to cyclic cryogenic treatment; the part is clamped on a mechanical arm, the mechanical arm is programmed and the movement track of the part is optimized; the powder is dried in a powder drying box and then loaded into a powder feeding tank, and a deposition layer with certain thickness is obtained through a supersonic laser deposition technology platform; the deposition layer is subjected to stress relief heat treatment; and machining is performed. The refractory metal part is repaired by using the supersonic laser deposition technology, the process is reasonable and easy to operate, the repairing effect is good, the deposition process integrates the cold characteristics of cold spraying and the advantages of laser heat, the prepared deposition layer has good bonding strength with the substrate, has the characteristics of no component change, controllable thickness and compactness, and the repaired part has excellent mechanical properties, and the cost is also low.

Description

Technical Field

[0001] This invention belongs to the field of surface remanufacturing technology and relates to a method for repairing refractory metal parts based on supersonic laser deposition technology. Background Technology

[0002] With the increasing demands on the technical specifications of rockets, high-temperature furnaces, engines, etc. in the field of military equipment and national economic life, higher requirements have been placed on the high-temperature resistance and other properties of equipment components. Using refractory metals (W, Nb, Mo, Ta, V, Re, etc.) with high melting points and excellent high-temperature properties can better meet the performance requirements. However, high-hardness refractory metal components are prone to wear and other failure modes due to long-term service in harsh environments. Compared with replacing new components, using a reliable surface remanufacturing technology for repair is a more economical and energy-saving effective means.

[0003] Currently, the main repair methods for refractory metals include laser cladding, thermal spraying, and cold spraying. Laser cladding and thermal spraying involve high-temperature melting of the coating / substrate, resulting in significant heat input. This leads to thermally induced adverse effects on the coating, such as phase transformation, dilution, and decomposition, impacting coating performance. Cold spraying, based on the plastic deformation (non-melting) of the material to achieve powder particle deposition, avoids the thermally induced adverse effects of laser cladding and thermal spraying. However, it places certain requirements on the plastic deformation capacity of the deposited material, especially in the deposition of high-hardness, low-plasticity materials like refractory metals. Due to the limited plastic deformation capacity of the powder particles, problems such as low deposition efficiency, poor coating density, and weak interfacial bonding arise. Furthermore, in cold spraying, expensive helium is typically used as the carrier gas to achieve sufficient deposition rates, and high requirements are placed on the characteristics of the deposited powder (such as morphology, particle size, and particle size distribution), significantly increasing costs and making it unsuitable for engineering production and application. Therefore, there is an urgent need to develop a low-cost, high-performance repair technology for refractory metal components.

[0004] Supersonic laser deposition technology, developed from cold spraying, utilizes a high-energy-density laser beam to instantaneously heat the sprayed particles and substrate material, enhancing the material's plastic rheology to control its plastic deformation capacity and deposition behavior. It is an effective method for depositing high-melting-point, brittle materials. As an emerging technology, currently published patents mainly focus on the development of deposition equipment, such as Chinese patent number 202120721537.2, "A Device for Repairing Corrosion on the Inner Wall of Pipelines Based on Supersonic Laser Deposition Technology." Applications of the deposited materials are rarely mentioned, especially the application of supersonic laser deposition technology in refractory metals, which has yet to be reported. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for repairing refractory metal parts based on supersonic laser deposition technology. It has the characteristics of reasonable process, good repair effect and low cost. The prepared deposition layer is dense and has good bonding strength with the substrate. The repaired parts have excellent mechanical properties.

[0006] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: a method for repairing refractory metal parts based on supersonic laser deposition technology, characterized by including the following steps:

[0007] 1) Degrease and roughen the surface of the refractory metal parts to be repaired;

[0008] 2) Select refractory metal powder with the same composition as the refractory metal parts and perform cyclic deep cryogenic treatment;

[0009] 3) The component to be repaired after step 1) is clamped onto the robotic arm using a tooling. The robotic arm is programmed to optimize the movement trajectory of the component so that the movement trajectory is consistent with the basic surface to be repaired, that is, the distance from the deposition point to the spray gun is always kept constant, and the tangent of the deposition point is always perpendicular to the spray gun.

[0010] 4) Place the powder processed in step 2) in a drying oven at 50-70°C for 0.5-2 hours, remove it and put it into a powder feeding tank. Then, using a supersonic laser deposition technology platform, use a spray gun and laser device to fix the powder and a robotic arm to move the components to deposit a layer of a certain thickness.

[0011] 5) Perform stress-relief heat treatment on the deposited layer obtained in step 4);

[0012] 6) Machining is performed on the deposited layer after step 5) to remove rough and excess surfaces and form a smooth surface that meets the requirements of component dimensional tolerance, form and position tolerance, and roughness.

[0013] Preferably, the refractory metal component in step 1) is composed of one or more of tungsten, niobium, molybdenum, tantalum, vanadium, and rhenium.

[0014] Furthermore, the surface to be repaired in step 1) can be a plane, a curved surface, or a complex surface composed of planes and curved surfaces.

[0015] Preferably, the roughening treatment in step 1) is sandblasting or laser roughening.

[0016] Furthermore, the refractory metal powder in step 2) is prepared by electro-explosion or plasma atomization, and the powder morphology is solid or porous spherical or near-spherical, with a particle size distribution range of 15μm to 45μm.

[0017] Furthermore, the process of the cyclic cryogenic treatment in step 2) is as follows: the refractory metal powder is kept at -150 to -100°C in a cryogenic treatment chamber for 5 to 15 minutes, then taken out and left to stand at room temperature for 5 ± 1 minutes, and this cycle is repeated 5 to 15 times; the refrigerant in the cryogenic treatment chamber is liquid nitrogen, and the temperature of the cryogenic treatment chamber is controlled by controlling the liquid nitrogen supply.

[0018] Furthermore, if the component to be repaired in step 2) is a thin-walled component, the clamping fixture should be designed to fit the component perfectly to avoid deformation.

[0019] Furthermore, the supersonic laser deposition technology platform in step 4) includes a cold spray system and a laser system. The carrier gas of the cold spray system is high-pressure nitrogen, with a pressure of 2-3 MPa and a temperature of 650-750°C. The laser of the laser system is a pulsed laser or a continuous laser, with a laser spot diameter of 4-8 mm.

[0020] Furthermore, the thickness of the deposited layer in step 4) is 0.2 mm to 5 mm.

[0021] Furthermore, the stress relief treatment in step 5) refers to: placing the product in a drying oven at 150-180℃ for 0.5-2 hours and then cooling it to room temperature with the oven.

[0022] Finally, the machining in step 6) includes, but is not limited to, one or more of turning, milling, grinding, CNC machining, and wire cutting.

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] 1. Since laser heating mainly acts on the substrate rather than the powder, the powder will not undergo a phase change during the deposition process. This maintains the low heat input deposition characteristics of cold spraying and can effectively avoid thermally induced adverse effects caused by high heat input.

[0025] 2. Through cyclic cryogenic treatment, the plasticity of the deposited powder is improved; the heating effect of the laser effectively softens the substrate material, increasing its plastic deformation capacity. Therefore, the prepared deposited layer is denser than that of a single cold spray coating, with higher deposition efficiency and controllable thickness.

[0026] 3. Due to the introduction of the laser heat source, nitrogen can be used instead of expensive helium as the carrier gas, thereby greatly reducing manufacturing costs and providing a high-performance and low-cost technical means for the repair of refractory metal parts.

[0027] 4. Stress-relief heat treatment: After slow cooling in the furnace, the internal stress of the deposited layer is slowly released, the machinability is improved, and the spalling phenomenon can be effectively avoided in the subsequent machining process.

[0028] This invention uses supersonic laser deposition technology to repair refractory metal parts. The process is reasonable and easy to operate, and the repair effect is good. The deposition process combines the "cold" characteristics of cold spraying and the "hot" advantages of laser. The prepared deposition layer has good bonding strength with the substrate, and has the characteristics of no change in composition, controllable thickness and density. The repaired parts have excellent mechanical properties, and the cost is also low. Attached Figure Description

[0029] Figure 1 This describes the morphology of Mo powder in Example 1 of the present invention;

[0030] Figure 2 (a) Figure 2 (b) shows the cross-sectional microstructure of the Mo deposition layer in Example 1. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] Example 1

[0033] In this embodiment, the refractory metal component to be repaired is a thin-walled Mo component. The specific steps of a method for repairing refractory metal components based on supersonic laser deposition technology are as follows:

[0034] 1) The damaged thin-walled Mo component has a concave curved surface to be repaired. The surface is degreased and laser roughened to obtain a rough surface with Ra = 10 μm ± 0.5 μm. The purpose of this step is to improve the bonding strength of the deposited layer.

[0035] 2) Solid spherical Mo powder prepared by the electro-explosion method was selected. Figure 1 The particle size distribution ranges from 17.18 μm to 42.06 μm, with an average particle size of approximately 28.90 μm. The powder was subjected to cyclic cryogenic treatment in a cryogenic chamber to improve its plasticity. Specifically, the supply of refrigerant (liquid nitrogen) was controlled to maintain the temperature at -150℃ for 10 minutes, then removed and allowed to stand at room temperature for 5 minutes. This cycle was repeated 12 times.

[0036] 3) The thin-walled Mo component processed in step 1) is clamped onto the robotic arm using a fully fitting fixture. The robotic arm is programmed using the concept of differentiation to divide the motion trajectory into several points, so that the motion trajectory is a curved surface that is basically consistent with the surface to be repaired. The distance from the deposition point to the spray gun is always kept at 40mm, and the tangent of the deposition point is always perpendicular to the spray gun.

[0037] 4) The Mo powder processed in step 2) is dried in a 60℃ drying oven for 1 hour to increase powder flowability. It is then removed and placed into a powder feeding tank. Deposition is performed using a supersonic laser deposition platform, employing a fixed spray gun and laser device with a robotic arm driving the component movement. The supersonic laser deposition platform includes a cold spray system and a laser system. The cold spray system uses high-pressure nitrogen as the carrier gas, with a pressure of 3 MPa and a temperature of 670℃. The laser system uses a continuous laser with a spot diameter of 8 mm. Since the deepest wear on the component is 1.2 mm, the deposition layer thickness is controlled at 1.25 mm to ensure the quality of the deposited repair layer. + 0 0.5 mm.

[0038] 5) Perform stress-relief heat treatment on the deposited layer obtained in step 4) to release some of the stress, thereby improving the material's machinability. Specifically, place it in a 150°C drying oven and keep it at that temperature for 2 hours, then cool it to room temperature with the furnace.

[0039] 6) The deposited layer after step 5) is machined to remove the rough and excess surface and form a smooth surface that meets the requirements of the part drawing (dimensional tolerance R220±0.2, roughness Ra3.2).

[0040] Performance tests were conducted on the component repaired in Example 1 and the sprayed sample, wherein the materials and processes of the sprayed sample were the same as those of the component.

[0041] XRD analysis showed that the Mo deposited layer had good phase consistency with the powder raw material and no oxidation phenomenon, indicating that the obtained deposited layer maintained the deposition characteristics of low heat input in cold spraying and had no thermal adverse effects. Figure 2 (a) Figure 2 (b) shows the microstructure of the cross-section of the deposited layer. It is evident that the Mo deposited layer is dense, without obvious cracks or pores. Table 1 shows the bonding strength and microhardness of the deposited layer. In the bonding strength test, all samples broke at the adhesive joint, with an adhesive strength of 70 MPa. Therefore, the bonding strength of the deposited layer is concluded to be >70 MPa. It is evident that the deposited layer obtained through supersonic laser deposition has high bonding strength with the substrate and a higher microhardness value than the original substrate. This indicates that the high deposition rate and high deposition point temperature during the deposition process caused deformation strengthening, resulting in superior mechanical properties after component repair.

[0042] Table 1 Microhardness and bonding strength of the sedimentary layers

[0043]

[0044] Example 2

[0045] In this embodiment, the refractory metal component to be repaired is a Ta component. The specific steps of a method for repairing refractory metal components based on supersonic laser deposition technology are as follows:

[0046] 1) The damaged Ta component has a local planar surface to be repaired. The local surface is degreased and roughened by sandblasting. Before sandblasting, hard tooling is used to protect the undamaged parts of the component, exposing only the damaged parts to avoid unnecessary processing. After sandblasting, a rough surface with Ra = 8μm ± 0.5μm is obtained. The purpose of this step is to improve the bonding strength of the deposited layer.

[0047] 2) Porous spherical Ta powder prepared by plasma atomization was selected, with a particle size distribution ranging from 15.18 μm to 40.34 μm and an average particle size of approximately 25.62 μm. The powder was placed in a cryogenic treatment chamber for cyclic cryogenic treatment to improve its plasticity. Specifically, the supply of refrigerant (liquid nitrogen) was controlled to maintain the temperature at -130℃ for 10 minutes, and then the powder was removed and allowed to stand at room temperature for 5 minutes. This cycle was repeated 10 times.

[0048] 3) The part processed in step 1) is clamped onto the robotic arm using a tooling. The movement trajectory is planar, and the distance from the deposition point to the spray gun is always kept at 30mm. The surface to be repaired is always perpendicular to the spray gun.

[0049] 4) The Ta powder processed in step 2) was dried in a 50°C drying oven for 1.5 hours to increase powder flowability. It was then removed and placed into a powder feeding container. Deposition was performed using a supersonic laser deposition technology platform, employing a fixed spray gun and laser device with a robotic arm driving the component movement. The supersonic laser deposition technology experimental platform includes a cold spray system and a laser system. The carrier gas for the cold spray system is high-pressure nitrogen, with a gas pressure of 2.5 MPa and a gas temperature of 720°C. The laser system uses a pulsed laser with a spot diameter of 4 mm. Due to localized component damage of 2.4 mm, the deposition layer thickness was controlled within...

[0050] 5) Perform stress-relief heat treatment on the deposited layer obtained in step 4) to release some of the stress, thereby improving the material's machinability. Specifically, place it in a 160°C drying oven and keep it at that temperature for 1.5 hours, then cool it to room temperature with the furnace.

[0051] 6) Mill the deposited layer after step 5) to remove rough and excess surfaces and form a smooth surface that meets the requirements of the part drawing (thickness dimension tolerance 20±0.2, roughness Ra3.2).

[0052] Performance tests were conducted on the component repaired in Example 2 and the sprayed sample, wherein the materials and processes of the sprayed sample were the same as those of the component.

[0053] The phase composition, microstructure, bonding strength and microhardness of the deposition layer in Example 2 are similar to those in Example 1.

[0054] Example 3

[0055] In this embodiment, the refractory metal component to be repaired is a Mo-5%Re component. The specific steps of a method for repairing refractory metal components based on supersonic laser deposition technology are as follows:

[0056] 1) The damaged Mo-5%Re component to be repaired is the flat surface at the bottom of the groove. The surface is degreased and roughened by sandblasting. Before sandblasting, the component wall is protected with hard tooling, exposing only the damaged bottom plane to avoid unnecessary processing. After sandblasting, a rough surface with Ra = 8μm ± 0.5μm is obtained. The purpose of this step is to improve the bonding strength of the deposited layer.

[0057] 2) Two powders, Mo and Re, prepared by the electro-explosion method, were used. A V-type mixer was used to mix the two powders at a ratio of 5% Re + the balance Mo for 3 hours. The Mo powder was a solid spherical powder with a measured particle size distribution range of 17.18 μm to 42.06 μm and an average particle size of approximately 28.90 μm. The Re powder was a solid near-spherical powder with a measured particle size distribution range of 16.06 μm to 40.11 μm and an average particle size of approximately 26.89 μm. The uniformly mixed powder was placed in a cryogenic treatment chamber for cyclic cryogenic treatment to improve its plasticity. Specifically, the supply of refrigerant (liquid nitrogen) was controlled to maintain the temperature at -130℃ for 10 minutes, then removed and allowed to stand at room temperature for 5 minutes. This cycle was repeated 10 times.

[0058] 3) The Mo-5%Re component processed in step 1) is clamped onto the robotic arm using a tooling. The movement trajectory is planar, and the distance from the deposition point to the spray gun is always kept at 45mm, and the surface to be repaired is always perpendicular to the spray gun.

[0059] 4) The Mo and Re powders processed in step 2) are dried in a 70℃ drying oven for 1.5 hours to increase powder flowability. They are then removed and placed into a powder feeding container. Deposition is performed using a supersonic laser deposition technology platform, employing a fixed spray gun and laser device with a robotic arm driving the component movement. The supersonic laser deposition technology experimental platform includes a cold spray system and a laser system. The carrier gas for the cold spray system is high-pressure nitrogen, with a gas pressure of 2.8 MPa and a gas temperature of 700℃. The laser system uses a continuous laser with a spot diameter of 4 mm. Due to a bottom plane damage of 0.8 mm, the deposition layer thickness is controlled within...

[0060] 5) Perform stress-relief heat treatment on the deposited layer obtained in step 4) to release some of the stress, thereby improving the material's machinability. Specifically, place it in a 170°C drying oven and keep it at that temperature for 2 hours, then cool it to room temperature with the furnace.

[0061] 6) Perform CNC machining on the deposited layer after step 5) to remove rough and excess surfaces and form a smooth surface that meets the requirements of the part drawing (depth dimension tolerance 12±0.2, roughness Ra6.3).

[0062] Performance tests were conducted on the component repaired in Example 3 and the sprayed sample, wherein the materials and processes of the sprayed sample were the same as those of the component.

[0063] The phase composition, microstructure, bonding strength and microhardness of the deposition layer in Example 3 are similar to those in Example 1.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for repairing refractory metal parts based on supersonic laser deposition technology, characterized in that... Includes the following steps: 1) Degrease and roughen the surface of the refractory metal parts to be repaired; 2) Select refractory metal powder with the same composition as the refractory metal parts and perform cyclic deep cryogenic treatment; The process of the cyclic cryogenic treatment is as follows: refractory metal powder is kept at -150 to -100°C in a cryogenic treatment chamber for 5 to 15 minutes, then taken out and left to stand at room temperature for 5 ± 1 minutes. This cycle is repeated 5 to 15 times. The refrigerant in the cryogenic treatment chamber is liquid nitrogen, and the temperature of the cryogenic treatment chamber is controlled by controlling the liquid nitrogen supply. 3) The component to be repaired after step 1) is clamped onto the robotic arm using a tooling. The robotic arm is programmed to optimize the movement trajectory of the component so that the movement trajectory is consistent with the basic surface to be repaired, that is, the distance from the deposition point to the spray gun is always kept constant, and the tangent of the deposition point is always perpendicular to the spray gun. 4) Place the powder processed in step 2) in a drying oven at 50-70°C for 0.5-2 hours, remove it and put it into a powder feeding tank. Then, using a supersonic laser deposition technology platform, use a spray gun and laser device to fix the powder and a robotic arm to move the components to deposit a layer of a certain thickness. The supersonic laser deposition technology platform includes a cold spray system and a laser system. The carrier gas of the cold spray system is high-pressure nitrogen, with a pressure of 2-3 MPa and a temperature of 650-750℃. The laser of the laser system is a pulsed laser or a continuous laser, with a laser spot diameter of greater than or equal to 4 mm and less than 8 mm. 5) Perform stress-relief heat treatment on the deposited layer obtained in step 4); The stress-relief heat treatment refers to: placing the product in a drying oven at 150-180℃ and keeping it at that temperature for 0.5-2 hours, then cooling it to room temperature with the oven. 6) Machining is performed on the deposited layer after step 5) to remove rough and excess surfaces and form a smooth surface that meets the requirements of component dimensional tolerance, form and position tolerance, and roughness.

2. The method for repairing refractory metal parts according to claim 1, characterized in that: The refractory metal component in step 1) is composed of one or more of tungsten, niobium, molybdenum, tantalum, vanadium, and rhenium.

3. The method for repairing refractory metal parts according to claim 1, characterized in that: The surface to be repaired in step 1) is a plane, a curved surface, or a complex surface composed of planes and curved surfaces.

4. The method for repairing refractory metal parts according to claim 1, characterized in that: The roughening treatment in step 1) can be either sandblasting or laser roughening.

5. The method for repairing refractory metal parts according to claim 1, characterized in that: The refractory metal powder in step 2) is prepared by electro-explosion or plasma atomization. The powder morphology is solid or porous spherical or near-spherical, and the particle size distribution ranges from 15μm to 45μm.

6. The method for repairing refractory metal parts according to claim 1, characterized in that: If the component to be repaired in step 2) is a thin-walled part, the clamping fixture should be designed to fit the component perfectly to avoid deformation.

7. The method for repairing refractory metal parts according to claim 1, characterized in that: The thickness of the deposited layer in step 4) is 0.2 mm to 5 mm.

8. The method for repairing refractory metal parts according to claim 1, characterized in that: The machining process in step 6) includes, but is not limited to, one or more of turning, milling, grinding, CNC machining, and wire cutting.

Images