Method for repairing defects in medium carbon cast steel structural parts

Abstract

The application provides a defect repairing method for medium-carbon cast steel structural parts, which comprises the following steps: providing a cold spraying powder, wherein the cold spraying powder comprises 40wt%-60wt% nickel-based metal powder, 30wt%-50wt% stainless steel metal powder and 10wt%-30wt% alumina powder; removing defects on the medium-carbon cast steel structural part to form a gap on the medium-carbon cast steel structural part; and cold spraying the cold spraying powder into the gap to form a repairing coating; wherein the angle between the sidewall of the gap and the surface normal at the upper edge of the gap is 45°-60°; and the particle size of the nickel-based metal powder is 3-10 microns. The repairing coating formed by the method of the application has low porosity and high bonding strength; meanwhile, the method can be used to repair devices with complex shapes or inconvenient to disassemble on site, thereby greatly reducing the processing difficulty, processing period and processing cost.

Description

Technical Field

[0001] The present invention relates to the technical field of metal repair, in particular to a defect repair method for a medium carbon cast steel structural part. Background Art

[0002] As global requirements for carbon emissions continue to increase, the goals of carbon peak and carbon neutrality have been integrated into the long-term planning of economic and social development. Clean, pollution-free, and low-emission nuclear energy is one of the most promising new energy sources. WCB carbon steel valves are widely used in the nuclear power field, but due to process problems in the production process, defects such as air holes are prone to occur; or under the repeated flushing of fluids, defects such as wear and cracks are prone to occur. If not promptly inspected and effective measures are not taken, serious hidden dangers will arise. Compared with replacing the entire component, patching and repairing the defective parts is simpler, more convenient, and more economical, and more in line with my country's carbon neutrality goals.

[0003] Currently, defect repair methods primarily include overlay welding and laser cladding. However, these methods require high-energy beam melting of the repair material and the base material, resulting in high heat input to the cast steel. Furthermore, during the repair process, medium-carbon cast steels like WCB develop a hardenable martensitic structure in the heat-affected zone, making cracks highly susceptible to formation.

[0004] Therefore, there is an urgent need to develop defect repair methods suitable for medium carbon cast steel structural parts. Summary of the Invention

[0005] Based on this, the present invention provides a defect repair method for medium-carbon cast steel structural parts with low heat input, low porosity of the repair layer and high bonding strength.

[0006] The specific technical solutions are as follows:

[0007] According to one aspect of the present invention, a method for repairing defects of a medium carbon cast steel structural member is provided, comprising the following steps:

[0008] Providing cold spray powder, wherein the cold spray powder comprises, by mass percentage, 40 wt% to 60 wt% of nickel-based metal powder, 30 wt% to 50 wt% of stainless steel metal powder, and 10 wt% to 30 wt% of aluminum oxide powder;

[0009] removing defects on a medium carbon cast steel structural member to form a notch on the medium carbon cast steel structural member; and

[0010] cold spraying the cold spray powder into the notch to form a repair coating;

[0011] The angle between the side wall of the notch and the surface normal at the upper edge of the notch is 45° to 60°; and the particle size of the nickel-based metal powder is 3 μm to 10 μm.

[0012] In one embodiment, the cold spray powder comprises, by mass percentage, 50 wt % to 60 wt % of nickel-based metal powder, 30 wt % to 40 wt % of stainless steel metal powder, and 10 wt % to 15 wt % of aluminum oxide powder.

[0013] In one embodiment, the particle size of the nickel-based metal powder is 3 μm to 5 μm.

[0014] In one embodiment, the particle size of the stainless steel metal powder is 5 μm to 15 μm;

[0015] Optionally, the particle size of the stainless steel metal powder is 5 μm to 10 μm.

[0016] In one embodiment, the particle size of the aluminum oxide powder is 10 μm to 20 μm.

[0017] In one embodiment, the depth of the notch is a, the wall thickness of the medium carbon cast steel structural member is b, and a≤0.25b is satisfied.

[0018] In one embodiment, after forming the notch and before forming the repair coating, the defect repair method further includes a step of polishing the notch to increase the surface roughness of the notch.

[0019] In one embodiment, the cold spraying is supersonic cold spraying, the accelerating gas of the cold spraying is compressed air, the temperature of the accelerating gas is 150°C~600°C, the pressure of the accelerating gas is 0.5Mpa~2.0Mpa, the spraying distance is 10mm~30mm, the spraying angle is 75°~90°, and the powder feeding rate is 10g / min~30g / min.

[0020] In one embodiment, the temperature of the accelerating gas is 450° C. to 550° C., the pressure of the accelerating gas is 2 MPa to 7 MPa, the spraying distance is 15 mm to 25 mm, and the spraying angle is 80° to 90°.

[0021] In one embodiment, the medium carbon cast steel structural component is a WCB carbon steel valve.

[0022] Compared with the traditional technology, the present invention has the following beneficial effects:

[0023] In the repair method of the present invention, the metal powder in the cold spray powder can provide good mechanical properties and corrosion resistance for the repair layer; the rebound compaction effect of the alumina ceramic powder and the pinning effect on the interface can further improve the density and bonding strength of the repair layer, reduce the porosity, and reduce the risk of clogging the spray gun during spraying. The use of nickel-based metal powder with a particle size of 3μm~10μm can ensure uniform powder transportation, thereby obtaining higher repair quality; the angle between the side wall of the gap and the surface normal at the upper edge of the gap is limited to 45°~60°, which can ensure the quality of the repair while forming a smaller gap; the use of cold spraying can reduce the input heat and reduce the thermal stress generated on the surface of the medium carbon cast steel structural part during the repair process. In addition, the method of the present invention can realize on-site repair of structural parts with complex shapes or inconvenient removal, greatly reducing the processing difficulty, processing time and processing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 Schematic diagram of the angle between the side wall of the notch and the surface normal at the upper edge of the notch;

[0026] Figure 2 This is a microstructure diagram of the repair coating in Example 1 of the present invention;

[0027] Figure 3 This is an appearance diagram of the repaired WCB carbon steel valve in Example 1 of the present invention;

[0028] Figure 4 This is an appearance diagram of a WCB carbon steel valve after on-site repair of damaged parts according to one embodiment of the present invention. DETAILED DESCRIPTION

[0029] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention will be described in detail. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. Unless otherwise specified, the various raw materials, reagents, instruments, and equipment used in the present invention may be purchased commercially or prepared by existing methods.

[0031] Herein, “preferred”, “better”, “more preferred” and “suitable” are merely used to describe implementation methods or examples with better effects. It should be understood that they do not constitute limitations on the scope of protection of the present invention.

[0032] In the present invention, “further”, “further”, “particularly”, etc. are used for descriptive purposes to indicate differences in content, but should not be understood as limiting the scope of protection of the present invention.

[0033] In the present invention, the terms "optionally," "optional," and "optional" mean optional or dispensable, i.e., they refer to either option being selected from two parallel options: "with" or "without." If a technical solution contains multiple "optional" clauses, each "optional" clause is independent unless otherwise specified and there are no conflicts or constraints.

[0034] Some embodiments of the present invention provide a method for repairing defects in a medium-carbon cast steel structural component.

[0035] In some embodiments, the above-mentioned repair method includes steps S100, S200 and S400.

[0036] S100, providing cold spray powder, wherein the cold spray powder comprises, by mass percentage, 40 wt% to 60 wt% of nickel-based metal powder, 30 wt% to 50 wt% of stainless steel metal powder, and 10 wt% to 30 wt% of aluminum oxide powder;

[0037] S200, removing defects on the medium carbon cast steel structural member to form a notch on the medium carbon cast steel structural member;

[0038] S400, cold spraying the cold spray powder into the notch to form a repair coating;

[0039] The angle between the side wall of the notch and the surface normal at the upper edge of the notch is 45° to 60°; and the particle size of the nickel-based metal powder is 3μm to 10μm.

[0040] In the present invention, medium carbon cast steel refers to carbon cast steel with a carbon content of 0.25% to 0.65%; particle size refers to the diameter of powder particles.

[0041] The present invention uses a mixture of metal powder and alumina ceramic powder as cold spray powder. The metal powder can improve the mechanical properties and corrosion resistance of the repair layer. The rebound compaction effect of the hard ceramic particles and the pinning effect on the interface can improve the density and bonding strength of the repair layer. In addition, the scouring effect of the ceramic particles can reduce the risk of spray gun clogging.

[0042] It is understandable that the method of the present invention can be used not only to repair crack defects on the surface of medium carbon cast steel structural parts, but also to repair other surface defects, including but not limited to scarring, folding, rust, etc.

[0043] In some embodiments, the cold spray powder comprises, by mass percentage, 50 wt % to 60 wt % of nickel-based metal powder, 30 wt % to 40 wt % of stainless steel metal powder, and 10 wt % to 15 wt % of aluminum oxide powder.

[0044] Preferably, the cold spraying powder comprises, by mass percentage, 55 wt % of nickel-based metal powder, 30 wt % of stainless steel metal powder and 15 wt % of aluminum oxide powder.

[0045] In some preferred examples, the particle size of the nickel-based metal powder is 3 μm to 5 μm.

[0046] In some embodiments, the particle size of the stainless steel metal powder is 5 μm to 15 μm; preferably, the particle size of the stainless steel metal powder is 5 μm to 10 μm.

[0047] In some specific examples, the stainless steel metal powder is 316L stainless steel metal powder.

[0048] In some embodiments, the particle size of the aluminum oxide powder is 10 μm to 20 μm.

[0049] It can be understood that controlling the particle size of nickel-based metal powder, stainless steel metal powder and alumina powder within a specific range can improve the quality of defect repair while ensuring uniform powder transportation; if the particle size is too small, the powder fluidity is poor, resulting in difficulty in transportation; if the particle size is too large, the powder acceleration effect is poor, resulting in a decrease in the quality of the repair layer.

[0050] In some embodiments, step S100 includes the following steps:

[0051] S101, providing raw materials for cold spraying powder according to the mass percentage of any one of the above embodiments;

[0052] S102, mixing the raw materials to obtain a powder mixture; the mixing speed is 30 rpm to 300 rpm, and the mixing time is 2 h to 8 h;

[0053] S103, drying the powder mixture at 80°C for 4 hours.

[0054] In some preferred examples, in step S102 , the mixing time is 4 hours to 6 hours.

[0055] In some embodiments, in step S200, defects of the medium carbon cast steel structural component are processed to remove defects such as cracks and rust to expose fresh metal.

[0056] In some embodiments, in step S200, the depth of the notch is a, the wall thickness of the medium carbon cast steel structural component is b, and a≤0.25b is satisfied.

[0057] In some embodiments, in step S200, the angle between the side wall of the notch and the surface normal at the upper edge of the notch is 45°~60°; preferably, the angle between the side wall of the notch and the surface normal at the upper edge of the notch is 45°~50°; more preferably, the angle between the side wall of the notch and the surface normal at the upper edge of the notch is 45°.

[0058] Figure 1 Schematic diagram of the angle between the side wall of the notch and the surface normal at the upper edge of the notch; a is the angle between the side wall of the notch and the surface normal at the upper edge of the notch

[0059] Understandably, when removing defects on medium carbon cast steel structural parts, the depth of the notch needs to be controlled to not exceed 1 / 4 of the wall thickness of the medium carbon cast steel structural parts; on the one hand, the structural parts can be avoided from fracture damage as much as possible; on the other hand, the amount of cold spray powder can be saved and the repair cost can be reduced.

[0060] Controlling the angle between the side wall of the notch and the surface normal at the upper edge of the notch to be 45°~60° can improve the repair quality when the notch grinding area is small; if the angle is too large, the grinding removal area will be too large, and if the angle is too small, it will be difficult to ensure the bonding quality between the side wall and the repair layer.

[0061] In some implementation methods, the above-mentioned repair method further includes step S300.

[0062] S300, grind the notch to increase the surface roughness of the notch.

[0063] In one specific example, in step S300, the surface roughness of the notch to be sprayed is increased by a sandblasting process.

[0064] In some embodiments, in step S400, the spraying method is supersonic cold spraying.

[0065] In some embodiments, in step S400, the accelerated gas sprayed is compressed air.

[0066] In some embodiments, in step S400, the temperature of the accelerating gas is 150°C~600°C, and the pressure of the accelerating gas is 0.5Mpa~2.0Mpa; preferably, the temperature of the accelerating gas is 450°C~550°C, and the pressure of the accelerating gas is 1.2Mpa~1.7Mpa; more preferably, the temperature of the accelerating gas is 550°C, and the pressure of the accelerating gas is 1.7Mpa.

[0067] In some embodiments, in step S400, the spraying distance is 10 mm to 30 mm; preferably 15 mm to 25 mm; more preferably 20 mm.

[0068] In some embodiments, in step S400, the spraying angle is 75° to 90°; preferably 80° to 90°; more preferably 90°.

[0069] In some embodiments, in step S400, the powder feeding rate is 10 g / min to 30 g / min, preferably 10 g / min.

[0070] The use of supersonic cold spraying minimizes heat input to the surface of structural components and reduces thermal stress on the surface. Supersonic cold spraying is a low-temperature solid-state deposition technology developed based on aerodynamics. Compared with traditional welding and currently developing laser repair technologies, supersonic cold spraying technology has lower heat input and higher efficiency. In addition, the supersonic cold spraying process is simple, the size of the spraying particle beam can be precisely controlled, and when used with portable equipment, it can achieve on-site repair of failed parts. Therefore, supersonic cold spraying shows good application prospects in the repair of a variety of scrap parts.

[0071] In addition, the use of supersonic cold spraying technology to repair crack damage defects in nuclear power WCB carbon steel valves can significantly reduce the thermal impact of the repair process on the WCB carbon steel substrate and avoid cracks during the repair process.

[0072] In some implementation methods, the above-mentioned repair method further includes step S500.

[0073] S500, processing the repair coating to its original appearance.

[0074] In one specific example, in step S500, a handheld grinder and a manual file are used to process the repair layer to its original shape.

[0075] In some embodiments, the medium carbon cast steel structural member is a WCB carbon steel valve. WCB carbon steel is a medium carbon cast steel with a carbon content of 0.3% to 0.5%.

[0076] The defect repair method for medium-carbon cast steel structural parts of the present invention adjusts the composition, ratio, and particle size of the spray powder, improves the defect processing method, and combines it with a cold spraying method to reduce the thermal stress generated during the spraying process, thereby achieving surface repair of WCB carbon steel valves. In addition, the repair method of the present invention is low-cost, simple and convenient to operate, and can be used for on-site repair of various accessories with complex shapes or inconvenient disassembly. Figure 4 The figure shows the structural parts after the damaged part of the WCB carbon steel valve is repaired on site by using the method of the present invention.

[0077] It is understandable that the method of the present invention can be used not only to repair WCB carbon steel, but also to repair other nuclear power equipment and medium carbon cast steel structural parts.

[0078] The present invention will be further described below with reference to specific examples and comparative examples, but they should not be construed as limiting the scope of protection of the present invention. Example 1

[0079] (1) Use a sieve to screen out nickel-based metal powder of 3μm~5μm, 316L stainless steel powder of 5μm~10μm, and alumina powder of 10μm~20μm.

[0080] (2) The required powders were weighed out in a ratio of 55 wt% nickel-based metal powder, 30 wt% 316L stainless steel powder, and 15 wt% alumina powder, and placed in an automatic powder mixer for mixing at a mixing speed of 30 rpm for 4 h.

[0081] (3) Pour out the mixed powder and dry it in an oven at 80°C for 4 h to obtain cold spray powder.

[0082] (4) Use a handheld grinder and a hand file to remove defects such as cracks and rust on the surface of the WCB carbon steel valve, exposing fresh metal on the surface. After removing the defects, the depth of the notch is about 4 mm (about 1 / 5 of the wall thickness), and the angle between the notch side wall and the surface normal at the notch top is 45°.

[0083] (5) Use masking tape to protect non-spraying areas.

[0084] (6) The supersonic cold spray solid deposition process is used for gap repair, in which the supersonic cold spray equipment is a low-pressure handheld type, the accelerating gas type is compressed air, the accelerating gas temperature is 550 ° C, the accelerating gas pressure is 1.7 MPa, the spraying distance is 20 mm, the spraying angle is 90 °, and the powder feeding rate is 10 g / min.

[0085] (7) After spraying, use a handheld grinder and a hand file to process the repair layer to the predetermined shape.

[0086] Figure 2 The cross-sectional microstructure of the repaired layer after repair; Figure 3 This is the appearance of the repaired WCB carbon steel valve. Example 2

[0087] (1) Use a sieve to screen out nickel-based metal powder of 3μm~5μm, 316L stainless steel powder of 5μm~10μm, and alumina powder of 10μm~20μm.

[0088] (2) The required powders were weighed out in a ratio of 50 wt% nickel-based metal powder, 40 wt% 316L stainless steel powder, and 10 wt% alumina powder, and mixed in an automatic powder mixer. The process parameters were: mixing speed 30 rpm, mixing for 6 h.

[0089] (3) Pour out the mixed powder and dry it in an oven at 80°C for 4 h to obtain cold spray powder.

[0090] (4) Use a handheld grinder and a hand file to remove defects such as cracks and rust on the surface of the WCB carbon steel valve, exposing fresh metal on the surface. After removing the defects, the depth of the notch is about 4 mm (about 1 / 5 of the wall thickness), and the angle between the notch side wall and the surface normal at the notch top is 45°.

[0091] (5) Use masking tape to protect non-spraying areas.

[0092] (6) The supersonic cold spray solid deposition process was used for gap repair. The supersonic cold spray equipment was a low-pressure handheld type, the accelerating gas type was compressed air, the accelerating gas temperature was 500 °C, the accelerating gas pressure was 1.5 MPa, the spraying distance was 20 mm, the spraying angle was 90°, and the powder feeding rate was 20 g / min.

[0093] (7) After spraying, use a handheld grinder and a hand file to process the repair layer to the predetermined shape. Example 3

[0094] (1) Use a sieve to screen out nickel-based metal powder of 5μm~10μm, 316L stainless steel powder of 10μm~15μm, and alumina powder of 10μm~20μm.

[0095] (2) The required powders were weighed out in a ratio of 40 wt% nickel-based metal powder, 50 wt% 316L stainless steel powder, and 10 wt% alumina powder, and placed in an automatic powder mixer for mixing at a mixing speed of 200 rpm for 6 h.

[0096] (3) Pour out the mixed powder and dry it in an oven at 80°C for 4 h to obtain cold spray powder.

[0097] (4) Use a handheld grinder and a hand file to remove defects such as cracks and rust on the surface of the WCB carbon steel valve, exposing fresh metal on the surface. After removing the defects, the depth of the notch is about 4 mm (about 1 / 5 of the wall thickness), and the angle between the notch side wall and the surface normal at the notch upper edge is 60°.

[0098] (5) Use masking tape to protect non-spraying areas.

[0099] (6) The supersonic cold spray solid deposition process is used for gap repair, in which the supersonic cold spray equipment is a low-pressure handheld type, the accelerating gas type is compressed air, the accelerating gas temperature is 550 ° C, the accelerating gas pressure is 1.7 MPa, the spraying distance is 20 mm, the spraying angle is 90 °, and the powder feeding rate is 10 g / min.

[0100] (7) After spraying, use a handheld grinder and a hand file to process the repair layer to the predetermined shape. Example 4

[0101] (1) Use a sieve to screen out nickel-based metal powder of 5μm~10μm, 316L stainless steel powder of 10μm~15μm, and alumina powder of 10μm~20μm.

[0102] (2) The required powders were weighed out in a ratio of 60 wt% nickel-based metal powder, 30 wt% 316L stainless steel powder, and 30 wt% alumina powder, and placed in an automatic powder mixer for mixing at a mixing speed of 300 rpm for 4 h.

[0103] (3) Pour out the mixed powder and dry it in an oven at 80°C for 4 h to obtain cold spray powder.

[0104] (4) Use a handheld grinder and a hand file to remove defects such as cracks and rust on the surface of the WCB carbon steel valve, exposing fresh metal on the surface. After removing the defects, the depth of the notch is about 4 mm (about 1 / 5 of the wall thickness), and the angle between the notch side wall and the surface normal at the notch upper edge is 60°.

[0105] (5) Use masking tape to protect non-spraying areas.

[0106] (6) The supersonic cold spray solid deposition process is used for gap repair, in which the supersonic cold spray equipment is a low-pressure handheld type, the accelerating gas type is compressed air, the accelerating gas temperature is 550 ° C, the accelerating gas pressure is 1.7 MPa, the spraying distance is 20 mm, the spraying angle is 90 °, and the powder feeding rate is 15 g / min.

[0107] (7) After spraying, use a handheld grinder and a hand file to process the repair layer to the predetermined shape. Example 5

[0108] (1) Use a sieve to screen out nickel-based metal powder of 3μm~5μm, 316L stainless steel powder of 10μm~15μm, and alumina powder of 10μm~20μm.

[0109] (2) The required powders were weighed out in a ratio of 40 wt% nickel-based metal powder, 30 wt% 316L stainless steel powder, and 30 wt% alumina powder, and placed in an automatic powder mixer for mixing at a mixing speed of 150 rpm for 8 h.

[0110] (3) Pour out the mixed powder and dry it in an oven at 80°C for 4 h to obtain cold spray powder.

[0111] (4) Use a handheld grinder and a hand file to remove defects such as cracks and rust on the surface of the WCB carbon steel valve, exposing fresh metal on the surface. After removing the defects, the depth of the notch is about 4 mm (about 1 / 5 of the wall thickness), and the angle between the notch side wall and the surface normal at the notch upper edge is 60°.

[0112] (5) Use masking tape to protect non-spraying areas.

[0113] (6) The supersonic cold spray solid deposition process is used for gap repair, where the supersonic cold spray equipment is a low-pressure handheld type, the accelerating gas type is compressed air, the accelerating gas temperature is 500 ° C, the accelerating gas pressure is 1.5 MPa, the spraying distance is 20 mm, the spraying angle is 90 °, and the powder feeding rate is 20 g / min.

[0114] (7) After spraying, use a handheld grinder and a hand file to process the repair layer to the predetermined shape.

[0115] Comparative Example 1:

[0116] The method is basically the same as Example 1, except that the ratio of cold spray powder is different: nickel-based metal powder is 70wt%, 316L stainless steel powder is 20wt%, and alumina powder is 10wt%.

[0117] Comparative Example 2:

[0118] The method is basically the same as Example 1, except that the particle size of the nickel-based metal powder is different: the particle size of the nickel-based metal powder is 15 μm to 30 μm.

[0119] Comparative Example 3:

[0120] It is basically the same as Example 1, with the only difference being the angle between the notch sidewall and the surface normal at the notch upper edge: the angle is 80°.

[0121] The process parameters of the repair methods of Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1.

[0122] Table 1

[0123]

[0124] Performance Testing

[0125] The pressure resistance and leakage of the repaired WCB carbon steel valves were tested using air (pressure 25 bar, pressure time 1 minute) and water (pressure 30 bar, pressure time 1 minute). The porosity of the repaired layer was tested in accordance with the international standard ASTM E2109-1, and the bonding strength of the repaired layer was tested in accordance with the national standard GB / T 8642-2002. The performance test results are shown in Table 2.

[0126] Table 2

[0127]

[0128] It can be seen from Comparative Examples 1 to 3 that the proportion of nickel-based metal powder in Comparative Example 1 is too high, while the proportion of stainless steel metal powder is low; the particle size of the nickel-based metal powder in Comparative Example 2 is relatively high; in Comparative Example 3, the angle between the normal of the notch side wall and the substrate surface is greater than 60°; the porosity of the repair coating formed after repair using the methods of Comparative Examples 1 to 3 is high, and the bonding strength between the repair coating and the substrate is relatively low.

[0129] As can be seen from Examples 1 to 5, the method of the present invention is used to repair defects in WCB carbon steel valves. The resulting repair coating has a porosity of less than 0.8%, a bonding strength with the substrate surface greater than 58 MPa, and no leakage when subjected to gas or liquid pressure, meeting the pressure test requirements of industrial valves.

[0130] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0131] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A defect repair method for a medium carbon cast steel structural member, characterized in that: The steps include: Providing cold spray powder, wherein the cold spray powder comprises, by mass percentage, 50 wt% to 60 wt% of nickel-based metal powder, 30 wt% to 40 wt% of stainless steel metal powder, and 10 wt% to 15 wt% of aluminum oxide powder; removing defects on a medium carbon cast steel structural member to form a notch on the medium carbon cast steel structural member; and cold spraying the cold spray powder into the notch to form a repair coating; Among them, the angle between the side wall of the notch and the surface normal at the upper edge of the notch is 45°~60°; the particle size of the nickel-based metal powder is 3μm~10μm; the particle size of the stainless steel metal powder is 5μm~15μm; the particle size of the alumina powder is 10μm~20μm.

2. The defect repair method of a medium carbon cast steel structural member according to claim 1, characterized in that: Calculated by mass percentage, the cold spraying powder includes 55 wt % of nickel-based metal powder, 30 wt % of stainless steel metal powder and 15 wt % of aluminum oxide powder.

3. The defect repair method of a medium carbon cast steel structural member according to claim 1, characterized in that: The particle size of the nickel-based metal powder is 3 μm to 5 μm.

4. The defect repair method of a medium carbon cast steel structural member according to any one of claims 1 to 3, characterized in that: The particle size of the stainless steel metal powder is 5 μm to 10 μm.

5. The defect repair method of a medium carbon cast steel structural member according to any one of claims 1 to 3, characterized in that: The depth of the notch is a, the wall thickness of the medium carbon cast steel structural member is b, and a≤0.25b is satisfied.

6. The defect repair method of a medium carbon cast steel structural member according to any one of claims 1 to 3, characterized in that: After forming the notch and before forming the repair coating, the defect repair method further includes a step of polishing the notch to increase the surface roughness of the notch.

7. The defect repair method of a medium carbon cast steel structural member according to any one of claims 1 to 3, characterized in that: The cold spraying is supersonic cold spraying, the accelerating gas of the cold spraying is compressed air, the temperature of the accelerating gas is 150°C~600°C, the pressure of the accelerating gas is 0.5Mpa~2.0Mpa, the spraying distance is 10mm~30mm, the spraying angle is 75°~90°, and the powder feeding rate is 10g / min~30g / min.

8. The defect repair method of a medium carbon cast steel structural member according to claim 7, characterized in that: The temperature of the accelerating gas is 450°C~550°C, the pressure of the accelerating gas is 1.2Mpa~1.7Mpa, the spraying distance is 15mm~25mm, and the spraying angle is 80°~90°.

9. The defect repair method of a medium carbon cast steel structural member according to any one of claims 1 to 3 and 8, characterized in that: The medium carbon cast steel structural component is a WCB carbon steel valve.

Images