A laser repair welding process for defects of tungsten alloy MIM products

Abstract

The present application relates to laser repair welding technical field, especially relates to a kind of laser repair welding repair process of tungsten alloy MIM product defect.The process includes the following steps: appearance detection is carried out to tungsten alloy product, identify defect type, the defect type includes at least one of gate recess, surface pit, surface bubble, local breakage, gate protrusion and material sticking;For gate recess, surface pit, surface bubble and local breakage defect, the defect area is cleaned or removed treatment, then cleaning and drying are carried out;For gate protrusion and material sticking defect, polishing treatment is carried out;Under protective atmosphere, the defect area after pretreatment is carried out multi-layer multi-pass repair welding using pulse laser;The repair welding area is sequentially cooled, polished and size appearance inspection.The present application can effectively repair the various defects of tungsten alloy MIM product, the size precision of repaired product is high, appearance consistency is good, and product qualification rate is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of laser welding repair technology, and in particular to a laser welding repair process for defects in tungsten alloy MIM products. Background Technology

[0002] During the sintering process, tungsten alloy MIM (metal injection molding) products are prone to defects such as gate depressions, surface pits, surface blistering, localized damage, gate protrusions, and material adhesion due to the process characteristics, leading to a reduced product yield. Traditional methods typically treat products with these defects as scrap, resulting in a significant waste of materials, energy, and labor costs. Therefore, there is an urgent need for a process method that can effectively repair these defects in tungsten alloy MIM products.

[0003] There are two main types of existing repair methods for tungsten alloy products. One type involves coating the defect area with a mixed powder repair material followed by secondary sintering. This method requires placing the entire product in a sintering furnace for re-sintering, which is not only energy-intensive and time-consuming, but also only applicable to green billets or semi-finished sintered billets, unable to repair finished products with established defects. Furthermore, secondary sintering carries the risk of overheating and deformation. The other type uses lasers to repair surface defects in metal castings. This typically involves covering the defect area with a repair material containing powder of the same composition before scanning and fusing it with a high-intensity laser. This method has a wide range of laser process parameters, not optimized for the high melting point and brittleness of tungsten alloys, and does not address differentiated pretreatment for defect types or post-weld shape control, making it unsuitable for the thin-walled precision structures and various unique defect types of MIM (Metal Injection Molding) products. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a laser welding repair process for defects in tungsten alloy MIM products, comprising the following steps: Step 1, Defect Identification and Classification: Perform visual inspection on tungsten alloy MIM products to identify defect types, including at least one of the following: gate depression, surface pit, surface blistering, localized damage, gate protrusion, and material adhesion. Step 2, Defect Pre-treatment: For defects such as gate depressions, surface pits, surface bubbles, and localized damage, clean or remove the defective areas, and then wash and dry them; for gate protrusions and material sticking defects, directly perform grinding and polishing treatment. Step 3, Laser Repair Welding: Under a protective atmosphere, pulsed laser is used to perform multi-layer, multi-pass repair welding on the pre-treated defect area. Tungsten alloy welding wire is used as the repair welding material. Step 4: Post-weld repair treatment: Cool the repaired area, grind and polish it, and inspect its dimensions and appearance in sequence.

[0005] Furthermore, in step two: For gate depressions, surface pits, and localized damage defects, use a steel brush to clean and remove loose material from the defective area, followed by ultrasonic cleaning and drying. For surface blistering defects, use abrasive belts to coarsely grind away the blisters until the dense substrate is exposed, and then perform ultrasonic cleaning and drying. For gate protrusions and material sticking defects, coarse grinding, fine grinding, and polishing are performed in sequence.

[0006] Furthermore, the ultrasonic cleaning uses anhydrous ethanol as the cleaning solution.

[0007] Furthermore, in step three, the process parameters of the pulsed laser are: laser power 200-800W, spot diameter 0.5-2.0mm, pulse frequency 1-50Hz, and pulse width 0.1-20ms.

[0008] Furthermore, the process parameters of the pulsed laser are: laser power 300-500W, spot diameter 0.5-1.0mm, pulse frequency 3-10Hz, and pulse width 3-10ms.

[0009] Furthermore, in step three, the thickness of a single layer of cladding in the multi-layer, multi-pass repair welding is 0.3–0.5 mm, the interlayer temperature is 200–400 °C, and the repaired area is 0.5–1.0 mm higher than the substrate surface after repair welding.

[0010] Furthermore, in step three, the protective atmosphere is argon.

[0011] Furthermore, in step four, the grinding and polishing includes: using abrasive belts to finely grind away the excess weld material, and then using vibration polishing or magnetic polishing to make the surface roughness of the weld repair area reach Ra≤1.6μm.

[0012] Furthermore, in step four, the dimensional appearance inspection includes: measuring the dimensions of the weld repair area using calipers or go / no-go gauges, wherein the deviation between the dimensions of the weld repair area and the design dimensions is within ±0.1mm.

[0013] Furthermore, in step four, the cooling is either natural cooling or argon-protected cooling to room temperature.

[0014] Compared with existing technologies, the laser welding repair process for defects in tungsten alloy MIM products provided by this invention employs differentiated pretreatment methods for different defect types. This effectively removes contamination layers and loose structures from defective areas, providing a clean interface for subsequent welding and ensuring the metallurgical bonding strength between the repair layer and the substrate. Multi-layer, multi-pass pulsed laser welding is used, and by controlling the heat input, the low-power, low-frequency pulsed laser, adapted to the characteristics of tungsten alloy materials, achieves precise local heating, effectively avoiding thermal damage and deformation to thin-walled MIM products. The multi-layer, multi-pass welding method ensures the density of the repaired area, preventing cracks and porosity. Cooling, polishing, and dimensional inspection effectively control the dimensional accuracy, surface quality, and appearance consistency of the repaired area. This invention forms a complete end-to-end repair solution from defect identification to final inspection, capable of repairing defective tungsten alloy MIM products into qualified products that meet usage requirements, significantly improving product qualification rate, reducing scrap rate, and saving production costs. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a diagram of the gate depression / surface pit repair process provided in Embodiment 1 of the present invention, where a is the defect before repair, b is after laser welding, and c is after fine grinding restoration; Figure 2 This is a diagram of the edge and corner repair process provided in Embodiment 2 of the present invention, where a is the defect before repair, b is after laser welding, and c is after fine grinding restoration; Figure 3 The diagram shows the surface blister repair process provided in Embodiment 3 of the present invention, where a is the selection of blister products, b is the grinding to expose the hollow area, c is the laser welding to fill the blister, d is the fine grinding to remove excess material, e is the polishing to restore the product, and f is the final product. Figure 4 This is a photograph of the actual object in Comparative Example 1 where excessive laser power caused the repair area to turn black and burn through. Figure 5 This is a photograph of the actual object in Comparative Example 2 where excessively high pulse frequency caused bubbles to appear in the repair area; Figure 6 This is a photograph of the actual object in Comparative Example 3 where the excessive pulse width resulted in burn-through in the repair area and an excessively large heat-affected zone. Figure 7 This is a comparison image of the actual object after the repair area is smooth and the heat-affected zone is narrow after the 7ms pulse width repair welding in Embodiment 1 of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] The laser welding system used in this embodiment of the invention is a commercially available pulsed laser welding device, and the protective atmosphere is high-purity argon (purity ≥ 99.99%). The tungsten alloy MIM product to be repaired is a high-density alloy product, wherein the high-density alloy product has tungsten as the matrix phase, and the tungsten mass percentage is 85%–98%; the alloy also includes a liquid phase binder phase, which is selected from any one or more combinations of nickel, iron, copper, and cobalt.

[0019] I. Specific Operating Procedures This invention discloses a laser welding repair process for defects in tungsten alloy MIM products, which is operated according to the following steps: (a) Defect identification and classification Defect identification is performed on tungsten alloy MIM products. First, visible defects on the product surface are identified through visual inspection (i.e., appearance inspection). Inspectors look for anomalies such as pits, bubbles, breaks, protrusions, material adhesion, or incomplete filling. For internal or subsurface defects that cannot be directly observed on the surface, non-destructive testing methods are used for supplementary inspection, including X-ray inspection, ultrasonic testing, or penetrant testing, to determine the location, size, and depth of the defects. The results of visual inspection and non-destructive testing are combined to identify the defect type, which includes at least one of the following: gate depression, surface pit, surface blister, localized breakage, gate protrusion, and material adhesion. Based on the defect type, size, location, and depth, a repair plan is determined.

[0020] The above-mentioned visual inspection and non-destructive testing methods are all conventional technical means in this field. Those skilled in the art can adapt to the shape, size and defect type of the product to be inspected and select one or more combinations of X-ray flaw detection, ultrasonic testing or penetrant testing to obtain parameters such as the location, size and depth of the defects.

[0021] (ii) Defect pretreatment The following standardized preprocessing methods are adopted for different types of defects: For gate depressions, surface pits, and localized damage defects: use a steel brush to remove loose material from the defective area (this step can be skipped if there is no loose material); then perform ultrasonic cleaning to remove surface oil, dust, and other impurities, and dry before welding repair. Anhydrous ethanol is preferred as the cleaning solution for ultrasonic cleaning, as it can improve the cleaning effect on oil stains.

[0022] For surface blistering defects: use abrasive belts to coarsely grind away the blisters until the dense substrate is exposed; then perform ultrasonic cleaning to remove surface oil, dust, and other impurities, and dry before welding repair. Anhydrous ethanol is preferred as the cleaning solution for ultrasonic cleaning.

[0023] For gate protrusions and material adhesion defects: coarse grinding, fine grinding, and polishing are performed sequentially using abrasive belts, without the need for laser welding. Coarse grinding uses P60-P120 mesh abrasive belts for semi-fine grinding, and fine grinding uses P150-P240 mesh abrasive belts for fine grinding. The above mesh size range represents the optimal process window for the high hardness of tungsten alloys: Too low a mesh size (below P60) results in high grinding efficiency but excessive surface roughness, which is detrimental to the fusion quality of subsequent welding; too high a mesh size (above P240) results in low grinding efficiency and is prone to causing microcracks on the tungsten alloy surface due to accumulated grinding heat. The specific mesh size can be adjusted according to the defect size and surface quality requirements.

[0024] (iii) Laser repair welding Repair welding was performed using a pulsed laser welding system under a high-purity argon protective atmosphere. Repair welding material: Use tungsten alloy welding wire of the same grade as tungsten alloy MIM products to ensure consistency of material composition.

[0025] Laser welding parameters: The laser power is 200–800W; the spot diameter is 0.5–2.0mm; the pulse frequency is 1–50Hz; and the pulse width is 0.1–20ms.

[0026] The repair welding operation includes: Multi-layer, multi-pass welding is employed, which refers to the following: for areas with significant depth or width to be repaired, multiple layers are stacked and clad along the depth direction of the repair area (multi-layer), and multiple weld passes are arranged horizontally in parallel within the same layer (multi-pass). The entire repair area is filled through this layer-by-layer, pass-by-pass accumulation method. The thickness of each layer in multi-layer, multi-pass welding is 0.3–0.5 mm. After each layer is completed, the interpass temperature is allowed to drop to 200–400°C before welding the next layer. After the repair welding is completed, the repair area protrudes 0.5–1.0 mm above the substrate surface to create a machining allowance. The laser repair welding uses a low heat input welding method to reduce the heat-affected zone and avoid overheating and deformation of the substrate.

[0027] (iv) Post-weld treatment Cooling: Allow to cool naturally or under argon protection to room temperature after welding.

[0028] Grinding and polishing: Use abrasive belts to grind away excess weld material; then use vibratory polishing or magnetic polishing to make the surface roughness of the weld repair area Ra≤1.6μm.

[0029] Dimensional and visual inspection: Dimensional inspection: The dimensions of the weld repair area were measured using calipers or go / no-go gauges. The deviation between the dimensions of the weld repair area and the design dimensions was found to be within ±0.1mm. Visual inspection: Visually inspect the surface of the weld repair area to confirm that there are no cracks, pores, or defects due to lack of fusion.

[0030] II. Implementation Examples Example 1 (Repair of gate depressions / surface pits) The tungsten alloy MIM product to be repaired is a high-density tungsten-nickel-iron alloy product. Visual inspection identified the defects as gate depression and surface pits.

[0031] (1) Defect pretreatment: Use a steel brush to clean and remove loose material from the defect area (skip if there is no loose material); then use anhydrous ethanol as the cleaning solution for ultrasonic cleaning to remove surface oil, dust and other impurities, and dry before welding.

[0032] (2) Laser repair welding: A pulsed laser welding system is used for repair welding under a high-purity argon protective atmosphere. The welding material is tungsten alloy welding wire of the same grade as the product. The laser repair welding parameters are: laser power 500W, spot diameter 0.7mm, pulse frequency 5Hz, pulse width 7ms. Multi-layer and multi-pass welding is adopted, with a single layer cladding thickness of 0.3-0.5mm, an interpass temperature of 200-400℃, and the repaired area is 0.5-1.0mm higher than the base surface after repair welding.

[0033] (3) Post-weld repair treatment: After the repair welding is completed, the surface is allowed to cool naturally to room temperature. The excess material of the repair welding is removed by fine grinding with a sanding belt, and then the fine sanding belt marks are removed by vibratory polishing (50Hz, 6 hours). Finally, the surface roughness is reduced to Ra≤1.6μm by magnetic polishing.

[0034] The process and results of welding repair are as follows: Figure 1 As shown, where Figure 1 Image a shows the repair of defects such as pre-gate depressions / surface pits. Figure 1 Image b shows the result of laser repair welding, where the defect area is filled and clad using multi-layer, multi-pulse lasers. Figure 1 Figure c shows the surface after the surface has been restored by removing the welding allowance and restoring the surface smoothness through belt grinding and vibratory polishing during the fine grinding and restoration stage.

[0035] Figure 1The results showed that the repaired product had a completely filled welded area without cracks, pores or lack of fusion defects, and the welded area was flush with the surrounding substrate. The dimensions of the welded area were within ±0.1mm of the design dimensions after dimensional inspection.

[0036] Example 2 (Repair of chipped edges and corners) The tungsten alloy MIM product to be repaired is a high-density tungsten-nickel-iron alloy product. Visual inspection identified the defect type as chipped edges and corners (local damage).

[0037] (1) Defect pretreatment: Use a steel brush to clean and remove loose material from the defect area; then use anhydrous ethanol as a cleaning solution for ultrasonic cleaning to remove surface oil, dust and other impurities, and dry it before welding.

[0038] (2) Laser repair welding: A pulsed laser welding system is used for repair welding under a high-purity argon protective atmosphere. The welding material is tungsten alloy welding wire of the same grade as the product. The laser repair welding parameters are: laser power 500W, spot diameter 0.7mm, pulse frequency 3Hz, pulse width 5ms. Multi-layer and multi-pass welding is adopted, with a single layer cladding thickness of 0.3-0.5mm, an interpass temperature of 200-400℃, and the repaired area is 0.5-1.0mm higher than the base surface after repair welding.

[0039] (3) Post-weld repair treatment: After the repair welding is completed, the surface is allowed to cool naturally to room temperature. The excess material of the repair welding is removed by fine grinding with 240# abrasive belt, and then the fine abrasive belt marks are removed by vibration polishing (50Hz, 4 hours). Finally, the surface roughness is reduced to Ra≤1.6μm by magnetic polishing.

[0040] The result of the welding repair is as follows Figure 2 As shown, where Figure 2 Product 'a' is a defective product with chipped edges or corners. Figure 2 b represents the laser repair stage, where multiple layers of multi-channel, multi-pulse lasers are used to progressively stack and fill the damaged edges to restore the original shape. Figure 2 c is the diagram after the fine grinding and restoration stage, in which the welding allowance is removed and the corner geometry is restored through belt grinding and vibratory polishing.

[0041] Figure 2 The results showed that the repaired product had a completely filled welded area, well restored corner contours, and no cracks, pores, or lack of fusion defects. The welded area was flush with the surrounding substrate. The dimensions of the welded area were within ±0.1mm of the design dimensions, and there were no cracks, pores, or lack of fusion defects on the surface.

[0042] Example 3 (Surface blister repair) The tungsten alloy MIM product to be repaired is a high-density tungsten-nickel-iron alloy product, and the defect type identified by visual inspection is surface blistering.

[0043] (1) Defect pretreatment: Use sanding belt to remove the bulging parts and expose the internal hollows. Sand until the dense matrix is ​​exposed. Then clean with a steel brush and blow with compressed air to remove dust and other impurities for the next step.

[0044] (2) Laser repair welding: A pulsed laser welding system is used for repair welding under a high-purity argon protective atmosphere. The welding material is tungsten alloy welding wire of the same grade as the product. The laser repair welding parameters are: laser power 500W, spot diameter 0.7mm, pulse frequency 5Hz, pulse width 7ms. Multi-layer and multi-pass welding is adopted, with a single layer cladding thickness of 0.3-0.5mm, an interpass temperature of 200-400℃, and the repaired area is 0.5-1.0mm higher than the base surface after repair welding.

[0045] (3) Post-weld repair treatment: After the repair welding is completed, the surface is allowed to cool naturally to room temperature. The excess material of the repair welding is removed by fine grinding with 240# abrasive belt, and then the fine abrasive belt marks are removed by vibration polishing (50Hz, 4 hours). Finally, the surface roughness is reduced to Ra≤1.6μm by magnetic polishing.

[0046] Key stages in the repair welding process, such as Figure 3 As shown, where Figure 3 a) In the stage of selecting products with surface bubbling defects, visual inspection is used to identify products with surface bubbling defects. Figure 3 b) is the stage of sanding with a belt to expose the internal hollow areas. This involves using a sanding belt to roughly grind away the bulging parts and expose the internal hollow areas, thus revealing the entire area to be repaired. Figure 3 c represents the laser welding stage for filling voids, where multiple layers of multi-channel pulsed lasers are used to fill and clad the voided areas layer by layer. Figure 3 d represents the fine grinding stage to remove excess solder, where the amount of solder repair material is removed by fine grinding with a belt abrasive. Figure 3 e represents the polishing and restoration stage, where surface smoothness is restored through vibratory polishing and magnetic polishing. Figure 3 f represents the final product, which is a finished product that meets the requirements for dimensional accuracy and appearance quality.

[0047] The results showed that the surface of the product repaired in this embodiment was smooth, the bubbling defect was eliminated, the welded area was flush with the surrounding substrate, and there were no cracks, pores or incomplete fusion defects. The dimensions met the design requirements, the overall appearance of the product was good, and it met the usage requirements.

[0048] Comparative Example 1 Using the same operating steps and parameters as in Example 1, the only difference being that the laser power was adjusted to 900W, the gate depression defect of the tungsten alloy MIM product of the same material as in Example 1 was repaired.

[0049] The results are as follows Figure 4As shown, excessively high laser power leads to a significant increase in the heat-affected zone, blackening around the repaired area, and burn-through defects in some products. Compared to Example 1, excessively high laser power results in excessive heat input, which easily causes thermal damage and deformation to thin-walled MIM products, significantly reducing the repair pass rate.

[0050] Comparative Example 2 Using the same operating steps and parameters as in Example 1, except that the pulse frequency was adjusted to 60Hz, the gate depression defect of the tungsten alloy MIM product of the same material as in Example 1 was repaired.

[0051] The results are as follows Figure 5 As shown: Excessive pulse frequency leads to heat buildup, insufficient stirring of the molten pool, bubble defects in the repair area, and poor surface quality. Compared to Example 1, excessively high pulse frequency easily causes heat buildup and bubbling (e.g., Figure 5 As shown in the red circle, the density and appearance quality of the repaired area do not meet the requirements.

[0052] Comparative Example 3 Using the same operating steps and parameters as in Example 1, except that the pulse width was adjusted to 25ms, the gate depression defect of the tungsten alloy MIM product of the same material as in Example 1 was repaired.

[0053] like Figure 6 As shown: Excessive pulse width leads to excessively high single-point heat input, causing burn-through in the repair area, a significant increase in the width of the heat-affected zone, and thermal damage marks on the back of the product. Compared to Example 1, when the pulse width is too large, the heat-affected zone widens, the workpiece is prone to deformation, blackening, or even burn-through, and the repair quality cannot be guaranteed. Figure 6 As shown, in Comparative Example 3, a 25ms pulse width was used for welding repair. The repaired area exhibited obvious burn-through defects, with collapsed cladding metal and blackened surrounding substrate, indicating that an excessively large pulse width led to excessively high single-point energy input. Figure 7 As shown, Example 1 uses a 7ms pulse width for repair welding. The repaired area has a smooth surface without burn-through, a narrow heat-affected zone, and good fusion between the weld layer and the substrate. The comparison of the two figures shows that when the pulse width is too large, the heat input is concentrated, which can easily cause local overheating, burn-through, and thermal damage. However, the pulse width range limited by this invention can achieve a smooth weld layer and a narrow heat-affected zone, ensuring the repair quality.

[0054] IV. Design Concept and Beneficial Effects of the Invention 1. Design Concept This invention addresses various unique defects commonly found in tungsten alloy MIM products during sintering, such as gate depressions, surface pits, surface blistering, localized damage, gate protrusions, and material adhesion. It proposes a complete, end-to-end repair solution, encompassing defect identification and classification, differentiated pretreatment, multi-layer, multi-pass pulsed laser repair welding, cooling, polishing, and dimensional and visual inspection. This invention abandons existing repair approaches such as overall secondary sintering, high-power continuous laser scanning, or argon arc welding. Instead, it employs a low-power pulsed laser parameter window adapted to the high melting point and brittleness of tungsten alloys, combined with standardized pretreatment methods for different defect types (welding and polishing) and post-welding shape control methods. This achieves precise, low-damage repair of tungsten alloy MIM products.

[0055] 2. Beneficial effects (1) This invention employs differentiated pretreatment methods for different defect types: for gate depressions, surface pits, and localized damage defects, steel brush cleaning followed by ultrasonic cleaning is used; for surface blistering defects, abrasive belt grinding is used to remove the blistering layer followed by cleaning; for gate protrusions and material adhesion defects, direct grinding and polishing are performed. This differentiated pretreatment method can effectively remove the contamination layer and loose structure in the defect area, providing a clean interface for subsequent welding and ensuring the metallurgical bonding strength between the repair layer and the substrate. In contrast, the existing mixed powder + sintering solution only simply cleans the defect area, and the general solution for laser casting only uniformly degreases, neither of which can remove the loose blistering layer on the product surface.

[0056] (2) This invention uses pulsed laser for multi-layer, multi-pass welding, abandoning the large molten pool and high heat input repair method of argon arc welding, thus avoiding problems such as overheating, contour melting, and overall deformation. By precisely controlling key parameters such as laser power, pulse frequency, and pulse width, a special process window adapted to the characteristics of tungsten alloy materials is formed. As shown in Comparative Examples 5-7, excessively high laser power will lead to an increase in the heat-affected zone, blackening, and burn-through; excessively high pulse frequency will lead to heat accumulation and blistering; and excessively large pulse width will lead to burn-through and thermal damage. The laser power range of 200-800W, pulse frequency of 1-50Hz, and pulse width of 0.1-20ms specified in this invention can achieve the best repair effect and effectively avoid the above defects. Multi-layer, multi-pass welding can reduce the heat input of a single layer, reduce thermal stress, and avoid crack formation. This process achieves precise local heating, effectively avoiding thermal damage and deformation of MIM thin-walled products, and ensuring the density of the repaired area.

[0057] (3) The present invention adopts a complete post-processing process of reserving allowance, graded grinding, and dimensional control, which effectively controls the dimensional accuracy, surface quality and appearance consistency of the repair area, and the surface roughness after repair reaches Ra≤1.6μm. It solves the problems of lack of shape control method after welding repair and poor consistency of appearance, size and weight between the repair area and the substrate in the prior art.

[0058] (4) The present invention forms a complete whole-process repair solution from defect identification to final inspection, which can repair defective tungsten alloy MIM products into qualified products that meet the requirements of use, significantly improve the product qualification rate, reduce the scrap rate, save production costs, and has high industrial application value.

[0059] Although this document frequently uses terms such as gate depression, surface pit, surface blistering, and localized damage defects, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser welding repair process for defects in tungsten alloy MIM products, characterized in that, Includes the following steps: Step 1, Defect Identification and Classification: Perform visual inspection on tungsten alloy MIM products to identify defect types, including at least one of the following: gate depression, surface pit, surface blistering, localized damage, gate protrusion, and material adhesion. Step 2, Defect Pre-treatment: For defects such as gate depressions, surface pits, surface bubbles, and localized damage, clean or remove the defective areas, and then wash and dry them; for gate protrusions and material sticking defects, directly perform grinding and polishing treatment. Step 3, Laser Repair Welding: Under a protective atmosphere, pulsed laser is used to perform multi-layer, multi-pass repair welding on the pre-treated defect area. Tungsten alloy welding wire is used as the repair welding material. Step 4: Post-weld repair treatment: Cool the repaired area, grind and polish it, and inspect its dimensions and appearance in sequence.

2. The laser welding repair process for defects in tungsten alloy MIM products according to claim 1, characterized in that, In step two: For gate depressions, surface pits, and localized damage defects, use a steel brush to clean and remove loose material from the defective area, followed by ultrasonic cleaning and drying. For surface blistering defects, use abrasive belts to coarsely grind away the blisters until the dense substrate is exposed, and then perform ultrasonic cleaning and drying. For gate protrusions and material sticking defects, coarse grinding, fine grinding, and polishing are performed in sequence.

3. The laser welding repair process for defects in tungsten alloy MIM products according to claim 2, characterized in that: The ultrasonic cleaning uses anhydrous ethanol as the cleaning solution.

4. The laser welding repair process for defects in tungsten alloy MIM products according to claim 1, characterized in that: In step three, the process parameters of the pulsed laser are: laser power 200-800W, spot diameter 0.5-2.0mm, pulse frequency 1-50Hz, and pulse width 0.1-20ms.

5. The laser welding repair process for defects in tungsten alloy MIM products according to claim 4, characterized in that: The process parameters of the pulsed laser are: laser power 300-500W, spot diameter 0.5-1.0mm, pulse frequency 3-10Hz, and pulse width 3-10ms.

6. The laser welding repair process for defects in tungsten alloy MIM products according to claim 1, characterized in that: In step three, the thickness of a single layer of the multi-layer, multi-pass welding is 0.3–0.5 mm, the interlayer temperature is 200–400 °C, and the welded area is 0.5–1.0 mm higher than the substrate surface after welding.

7. The laser welding repair process for defects in tungsten alloy MIM products according to claim 1, characterized in that: In step three, the protective atmosphere is argon.

8. The laser welding repair process for defects in tungsten alloy MIM products according to claim 1, characterized in that: In step four, the grinding and polishing includes: using abrasive belts to remove the excess weld material, and then using vibration polishing or magnetic polishing to make the surface roughness of the weld repair area reach Ra≤1.6μm.

9. The laser welding repair process for defects in tungsten alloy MIM products according to claim 1, characterized in that: In step four, the dimensional appearance inspection includes: measuring the dimensions of the weld repair area using calipers or go / no-go gauges, wherein the deviation between the dimensions of the weld repair area and the design dimensions is within ±0.1mm.

10. The laser welding repair process for defects in tungsten alloy MIM products according to claim 1, characterized in that: In step four, the cooling is either natural cooling or argon-protected cooling to room temperature.

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