Method for restraining'hole-shaped 'defect in cutter ring laser cladding diamond composite coating

Abstract

The invention belongs to the technical field of laser additive manufacturing of diamond composite materials, and particularly relates to a low-defect laser cladding method of a diamond reinforced metal-based alloy composite coating and application of the low-defect laser cladding method in a shield hob ring. The method comprises the following steps: by taking diamond with a clean and dry surface as a treatment object, preparing diamond with a tungsten plating layer or a titanium plating layer through magnetron sputtering, and recording the diamond as a material A; then plating a second coating layer on the material A by adopting chemical plating, wherein the material of the second coating layer is selected from at least one of Co, Ni and Cu; after chemical plating is completed, in a vacuum atmosphere, heat preservation is conducted for 30-90 min at the temperature of 900-980 DEG C, and standby powder with the particle size being 95-106 micrometers is obtained; the standby powder and the metal bonding powder are contained in different stock bins respectively; and printing parameters are controlled for laser cladding printing, and a product is obtained. According to the method, the number of hole-shaped defects in the laser cladding diamond composite coating of the cutter ring is efficiently inhibited for the first time, and the size of the hole-shaped defects is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of laser additive manufacturing of diamond composite materials, and particularly relates to a low-defect laser cladding method for a diamond-reinforced metal-based alloy composite coating and application of the low-defect laser cladding method to a shield cutter ring. BACKGROUND

[0002] With large-scale construction of urban rail transit, water tunnel and cross-sea tunnel projects in China, shield tunneling technology is facing increasingly severe challenges. As a core component for directly crushing rock-soil bodies, the shield cutter ring has an extremely complex service environment and needs to withstand high stress impact, severe abrasive wear and strong corrosion and other multiple coupling effects. The traditional cutter ring materials (such as alloy steel 42CrMo) and the overall heat treatment process have been difficult to meet the long-life and high-reliability tunneling requirements in hard rock strata such as granite and quartzite, and frequent replacement due to cutter ring wear and failure not only greatly increases construction costs, but also seriously restricts the tunneling efficiency.

[0003] Laser cladding technology, as an advanced surface modification technology, has the characteristics of controllable heat input, metallurgical bonding between the coating and the substrate, low dilution rate and the ability to process complex curved surfaces, and provides an ideal solution for preparing high-performance wear-resistant coatings on the cutter ring surface. By cladding a layer of wear-resistant composite material on the cutter ring substrate, a gradient functional structure of "surface toughness and heart toughness and plasticity" can be achieved, which can improve the cutter ring life by several times without significantly increasing the cost.

[0004] In recent years, composite coatings with diamond as the reinforcing phase and high-entropy alloys, metal ceramics and the like as the substrate have shown great application potential. Diamond, as the hardest and most thermally conductive material known in nature, can significantly improve the hardness and wear resistance of the coating, and is theoretically very suitable for shield cutter rings under extreme abrasive wear conditions. However, in the process of laser cladding to prepare diamond-reinforced composite coatings, there are serious technical challenges:

[0005] First, the thermal physical properties of diamond are very different from those of the metal substrate. Its ultra-high thermal conductivity (~2000 W / (m·K)) makes it play the role of "heat sink" in the laser molten pool, which severely disturbs the heat flow distribution inside the molten pool, leading to instability of the molten pool temperature field and abnormal cooling and solidification behavior. This easily induces a unique "cave-like" porosity defect around the diamond particles. The defect has a special morphology, and the pores are usually closely wrapped or adjacent to the diamond particles. The formation of the pores is not due to traditional process pores or shrinkage pores, but is caused by local melt supercooling, gas trapping and interfacial wettability change due to instantaneous heat absorption of diamond.

[0006] Secondly, the inherent poor physical compatibility (poor wettability) and chemical inertness between diamond and metal matrix result in weak interfacial bonding strength. More seriously, the huge difference in thermal expansion coefficient between the two (diamond: ~1x10 -6 / K; metal matrix: ~14x10 -6 / K) will generate significant tensile stress during the rapid cooling process of the cladding layer, which not only aggravates the formation of "cave-like" pores, but also easily initiates micro-cracks at the interface.

[0007] The existence of these defects ("cave-like" pores and micro-cracks) seriously damages the compactness and continuity of the coating, becomes a stress concentration source, and easily expands into macro-cracks under the action of complex alternating load in the well, resulting in premature peeling failure of the coating. They are like "time bombs" that not only fail to play the strengthening role of diamond, but also make the wear resistance, impact resistance and fatigue life of the coating significantly lower than that of ordinary coating without diamond, completely deviating from the original intention of design.

[0008] Currently, researchers at home and abroad try to improve the interface bonding and quality by optimizing laser process parameters (such as adjusting power, scanning speed), pre-metallizing plating of diamond (such as Ti, Cr plating) and other methods. However, these methods do not mention how to solve the "cave-like" pore defects. Therefore, developing a new method that can efficiently inhibit the formation of "cave-like" defects in laser cladding diamond coating has great engineering significance and economic value for promoting the application of superhard composite coating in shield cutter ring and other high-value components. SUMMARY

[0009] The technical problem to be solved by the present application is that during the preparation of diamond reinforced metal matrix alloy composite coating by laser cladding, the temperature field distortion and rapid solidification behavior caused by the ultra-high thermal conductivity (2000 W / (m·K)) of diamond lead to the formation of high-density "cave-like" defects containing diamond in the coating, resulting in the industry-wide problems of reduced interfacial bonding strength, shortened wear life and reduced service life.

[0010] During the further research based on the patent 2025110888648, it was found that the use of a second cladding layer such as appropriately chemical plated Co and special heat treatment can further reduce the number of "cave-like defects" in high-density diamond-containing products.

[0011] The present application improves the wettability between diamond and metal binder phase by plating two cladding layers on the surface of diamond, changes the thermal conductivity state of diamond, and reduces the diffusion of diamond C atoms. Then, diamond reinforced metal matrix composite coating is prepared by laser cladding, and the number of defects in different plated diamond composite powders, including the number of "cave-like defects", is compared.

[0012] This invention discloses a method for suppressing "cavitation" defects in laser-clad diamond composite coatings, comprising the following steps:

[0013] Step 1

[0014] Using clean and dry diamond as the processing object, diamond with tungsten or titanium coating is prepared by magnetron sputtering, denoted as material A;

[0015] Step Two

[0016] A second coating layer is deposited on material A by chemical plating. The material of the second coating layer is selected from at least one of Co, Ni, and Cu. After the chemical plating is completed, the material is kept at 900~980℃, preferably 940~960℃, for 30~90min, preferably 50~75min under a vacuum atmosphere to obtain a spare powder with a particle size of 95~106 μm.

[0017] Step 3

[0018] The spare powder and metal bonding powder are placed in separate hoppers; the carrier gas flow rate for both the spare powder and metal bonding powder is controlled at 8-12 L / min, and laser cladding printing is performed to obtain the product.

[0019] During laser cladding printing, the laser power is controlled at 1200W~1800W, the scanning speed is 7~16mm, the spot diameter is between 2.5-4mm, the carrier gas is argon, the powder feeding rate of the spare powder is 1.8~2g / min, and the powder feeding rate of the metal bonding powder is 6~8g / min.

[0020] In this invention, clean and dry diamond is used as the target material. The first layer is prepared by magnetron sputtering on the surface of the target material. Specifically, high-purity tungsten or Ti is used as the target material, and the target material is coated at a temperature of 300-400℃. The protective atmosphere is argon, and the vacuum degree of the deposition chamber is controlled at ≤10. -1 Pa, deposition rate of 45~55 nm / min; to obtain a first coating layer with a thickness of 100-200 nm.

[0021] The thickness of the first coating layer is preferably 50-200 nm, and more preferably 100-200 nm.

[0022] In this invention, the concentration of the raw material salt in the plating solution used for electroless plating is 30-40 g / L, and the raw material salt is selected from at least one of water-soluble cobalt salt, water-soluble nickel salt, and water-soluble copper salt.

[0023] The preferred water-soluble cobalt salt is selected from at least one of cobalt chloride and cobalt nitrate.

[0024] The preferred water-soluble nickel salt is selected from at least one of nickel chloride, nickel nitrate, and nickel sulfate.

[0025] The preferred water-soluble copper salt is selected from at least one of copper sulfate and copper chloride.

[0026] In this invention, during electroless plating, the reducing agent solution is added to the plating bath dropwise while stirring. The concentration of the reducing agent in the solution is 20-40 g / L. The amount of reducing agent used is adjusted according to requirements, only needing to obtain a second coating with a thickness of 5-10 micrometers. In this invention, the reducing agent is preferably hypophosphite and / or hypophosphate.

[0027] In this invention, the hypophosphite is selected from at least one of sodium hypophosphite and calcium hypophosphite.

[0028] Preferably, the chemical plating solution designed in this invention also contains a complexing agent. The function of the complexing agent is to prevent the precipitation of elements such as Co and control their exudation; the complexing agent is selected from at least one of citric acid, malic acid, succinic acid, and acetic acid, and the concentration is preferably 0.03-0.2 mol / ml.

[0029] Preferably, the electroless plating solution designed in this invention also contains a stabilizer. The stabilizer can be a lead compound such as lead nitrate or a cadmium compound such as cadmium nitrate, and its concentration is 1-5 ppm.

[0030] Preferably, the chemical plating solution designed in this invention has a pH value of 8-10. More preferably, the pH value is controlled to 8-10 by adding acid or alkali during the plating process.

[0031] Preferably, the electroless plating temperature of the present invention is 30-90℃.

[0032] Preferably, the thickness of the second coating layer in this invention is 5-10 μm.

[0033] In industrial applications, before electroless plating, the tungsten-plated diamond powder is cleaned in distilled water or anhydrous ethanol for 3-10 minutes to remove surface impurities. Then, the dried powder is placed in a concentrated sulfuric acid solution (3.6-3.8 mol / L) for 5-10 minutes for roughening. After drying, it is activated by ultrasonic reaction in a solution of 30 g / L stannous chloride and 2.5 g / L palladium chloride for 5-10 minutes (ultrasonic frequency 100-150 kHz). The pretreated powder is then immersed in an electroless plating solution containing a second coating element, such as water-soluble cobalt salt, water-soluble nickel salt, or water-soluble copper salt. The powder is then immersed in the electroless plating solution to form a coating. The immersion time is not limited, as long as a thin film of 5-10 μm thickness is formed. The concentration of the plating solution is preferably between 30-40 g / L. The reducing agent used in this invention only needs to have the effect of reducing and precipitating Co, Ni, and Cu, and hypophosphite such as hypophosphite, sodium hypophosphite, and potassium hypophosphite can be selected. The role of the complexing agent is to prevent the precipitation of elements such as Co and control their precipitation, such as citric acid, malic acid, succinic acid, and acetic acid, with a preferred concentration of 0.03-0.2 mol / ml. The stabilizer can be lead nitrate or cadmium nitrate. The pH adjuster can be conventional acids such as hydrochloric acid and nitric acid, or bases such as sodium hydroxide, with a pH range of 8-10. The electroless plating temperature is preferably 30-90℃. After plating, conventional post-treatment methods such as water washing or acid washing can be used to remove unwanted substances from the powder. Finally, the dried coated powder is placed in a vacuum tube furnace and held at a temperature of 900-980℃ for 30-90 minutes, and then vacuum sealed for storage. During heating, the vacuum degree is 10. -1 -10 -3 Pa.

[0034] After the chemical plating of the second coating layer is completed, the powder is held at 900-980℃ in a vacuum environment for 30-90 minutes. This further achieves "degassing and / or impurity removal," optimizing the microstructure of the powder and thus further reducing the probability of "cavity defects" formation. During heating, gases (such as H2, N2, and water vapor) and low-boiling-point impurities (such as residual solvents, surfactants, and volatile salts) adsorbed inside or on the surface of the powder are "activated," and the low pressure of the vacuum environment accelerates the escape of these substances, achieving "purification" and "densification pretreatment" of the powder. This provides the necessary conditions for minimizing the number and size of individual "cavity defects" during subsequent printing.

[0035] As a further optimization, after chemical plating, under a vacuum atmosphere, the temperature is first raised to 300-400℃ at a heating rate of 5-10℃ / min and held for 10-20 min, then raised to 900-980℃, preferably 940-960℃, and held for 30-90 min, more preferably 50-75 min, to obtain a spare powder with a particle size of 95-106 μm. This can further reduce the number of "cavity" defects in the product and reduce the size of individual defects. The diamond particle size after plating is 90-106 μm.

[0036] The particle size range of the metal binder is 45-150 μm. The metal binder includes a high-entropy alloy; the high-entropy alloy is an FeCoCrNiAl high-entropy alloy.

[0037] This invention integrates technologies such as diamond coating design, laser power-scanning speed synergistic optimization, and real-time feedback control of molten pool temperature field. It effectively suppresses cavitation pores in the diamond composite coating of the shield cutter ring, significantly improves other defects, effectively enhances the coating's strength and chemical stability, and extends its service life. Attached Figure Description

[0038] Figure 1 Schematic diagram of composite coating on diamond surface

[0039] Figure 2 A schematic diagram of common cavity-like defects in laser-clad diamond coatings;

[0040] Figure 3 Here is a scanning electron microscope image of a typical cavity-like defect in Comparative Example 1;

[0041] Figure 4 The image shows a SEM image (two fields of view) of the WCo diamond composite coating obtained in Example 1.

[0042] Figure 5 SEM images (two fields of view) of the WCo diamond composite coating obtained in Comparative Example 2.

[0043] Figure 6 SEM images (two fields of view) of the WCo diamond composite coating obtained in Comparative Example 3.

[0044] Specific implementation methods

[0045] Example 1:

[0046] WCo composite coated diamond: The first coating layer was prepared by magnetron sputtering. High-purity tungsten target material (initial purity greater than 99.99%) was used to coat the diamond (average particle size 90-100 micrometers) at 350℃. The protective atmosphere was argon, and the vacuum level in the deposition chamber was controlled at ≤10. -1Pa, with a deposition rate of 45~55nm / min, yields a first coating layer with a thickness of 100-200nm.

[0047] The second coating layer is electroless plating. Before electroless plating, the tungsten-plated diamond powder is ultrasonically cleaned in distilled water for 5 minutes, and then ultrasonically cleaned in anhydrous ethanol for 5 minutes (ultrasonic frequency 100-150kHz) to remove surface impurities. Then, the dried powder is placed in a concentrated sulfuric acid solution (concentration 3.6mol / L) for roughening treatment at room temperature. After drying, it is placed in a solution of 30 g / L stannous chloride and 2.5 g / L palladium chloride for ultrasonic reaction for 5-10 minutes (ultrasonic frequency 100-150kHz) at room temperature for activation treatment. The pretreated powder is then placed in an electroless plating solution of cobalt sulfate. The powder to be coated is immersed in the electroless plating solution to form a film. The immersion time is not limited, as long as a film with a thickness of 5-10μm is formed. The concentration of the plating solution is 30-40g / L (maintained during plating), and the reducing agent hypophosphite (concentration 0.1mol / L) is introduced dropwise during plating. The plating solution contains a complexing agent, citric acid, preferably at a concentration of 0.1 mol / ml. It also contains a stabilizer, lead nitrate. During the electroless plating process, the pH is controlled at 8.8–9.2 (adjusters can be conventional acids such as hydrochloric acid or nitric acid, or alkalis such as sodium hydroxide). The preferred electroless plating temperature is 80℃. After plating, conventional post-treatment methods such as water washing or acid washing can be used to remove unwanted substances from the powder. Finally, the dried coated powder is placed in a vacuum tube furnace and held at 950℃ for 60 minutes (vacuum degree 10). -3 -10 -1 Pa), vacuum sealed and stored, to obtain Composite coated diamond.

[0048] Laser additive manufacturing process: laser power is 1400W, scanning speed is 7mm / s, and diamond is... The composite coated diamond has a particle size of 90~106μm, and the metal-based alloy binder powder has a particle size of 45~150μm (the metal-based alloy binder is made of FeCoCrNiAl). The substrate preheating temperature is 200℃, and the cavity defects are basically eliminated. During printing... The carrier gas flow rate for the composite coated diamond is 8 L / min, and the carrier gas flow rate for the metal-based alloy binder powder is 10 L / min; the powder is fed and printed simultaneously. The feed rate of diamond for the composite coating is 1.9 g / min; the feed rate of metal-bonded powder is 7 g / min.

[0049]

[0050] In Table 1, the quantity interval refers to the maximum and minimum values ​​of the number of pitted defects at 5 different locations, each with an area of ​​50 square millimeters (magnification of 200x). The average value is calculated as: the sum of the number of all pitted defects at the 5 different locations / 5.

[0051] The characterization diagram of the WCo diamond composite coating obtained in Example 1 is shown below. Figure 4 .

[0052] Example 2:

[0053] WCo composite coated diamond: The first coating layer was prepared by magnetron sputtering. High-purity tungsten target material (initial purity greater than 99.99%) was used to coat the diamond (average particle size 90-100 micrometers) at 350℃. The protective atmosphere was argon, and the vacuum level in the deposition chamber was controlled at ≤10. -1 Pa, with a deposition rate of 45~55nm / min, yields a first coating layer with a thickness of 100-200nm.

[0054] The second coating layer is electroless plating. Before electroless plating, the tungsten-plated diamond powder is ultrasonically cleaned in distilled water for 5 minutes, and then ultrasonically cleaned in anhydrous ethanol for 5 minutes (ultrasonic frequency 100-150kHz) to remove surface impurities. Then, the dried powder is placed in a concentrated sulfuric acid solution (concentration 3.6mol / L) for roughening treatment at room temperature. After drying, it is placed in a solution of 30 g / L stannous chloride and 2.5 g / L palladium chloride for ultrasonic reaction for 5-10 minutes (ultrasonic frequency 100-150kHz) at room temperature for activation treatment. The pretreated powder is then placed in an electroless plating solution of cobalt sulfate. The powder to be coated is immersed in the electroless plating solution to form a film. The immersion time is not limited, as long as a film with a thickness of 5-10μm is formed. The concentration of the plating solution is 30-40g / L (maintained during plating), and the reducing agent hypophosphite (concentration 0.1mol / L) is introduced dropwise during plating. The plating solution contains a complexing agent, citric acid, preferably at a concentration of 0.1 mol / ml. It also contains a stabilizer, lead nitrate. During the electroless plating process, the pH is controlled at 8.8–9.2 (adjusters can be conventional acids such as hydrochloric acid or nitric acid, or alkalis such as sodium hydroxide). The preferred electroless plating temperature is 80℃. After plating, conventional post-treatment methods such as water washing or acid washing can be used to remove unwanted substances from the powder. Under a vacuum atmosphere, the temperature is first increased to 350℃ at a rate of 5℃ / min and held for 20 min (this temperature is consistent with the magnetron sputtering tungsten plating temperature), then increased to 950℃ at a rate of 5℃ / min and held for 75 min to obtain a ready-made powder with a particle size of 95–106 μm.

[0055] Laser additive manufacturing process: completely consistent with Example 1. The number of pitting defects per 50 square millimeters of the obtained WCo diamond composite coating is shown in Table 1, and the crack situation within the 50 square millimeter view frame is shown in Table 1.

[0056] Example 3: WCo Composite Coated Diamond: The first coating layer was prepared by magnetron sputtering. High-purity tungsten target material (initial purity greater than 99.99%) was used to coat the surface of diamond (average particle size 90-100 micrometers) at 350°C. The protective atmosphere was argon, and the vacuum level in the deposition chamber was controlled at ≤10. -1 Pa, with a deposition rate of 45~55nm / min, yields a first coating layer with a thickness of 100-200nm.

[0057] The second coating layer is electroless plating. Before electroless plating, the tungsten-plated diamond powder is ultrasonically cleaned in distilled water for 5 minutes, and then ultrasonically cleaned in anhydrous ethanol for 5 minutes (ultrasonic frequency 100-150kHz) to remove surface impurities. Then, the dried powder is placed in a concentrated sulfuric acid solution (concentration 3.6mol / L) for roughening treatment at room temperature. After drying, it is placed in a solution of 30 g / L stannous chloride and 2.5 g / L palladium chloride for ultrasonic reaction for 5-10 minutes (ultrasonic frequency 100-150kHz) at room temperature for activation treatment. The pretreated powder is then placed in an electroless plating solution of cobalt sulfate. The powder to be coated is immersed in the electroless plating solution to form a film. The immersion time is not limited, as long as a film with a thickness of 5-10μm is formed. The concentration of the plating solution is 30-40g / L (maintained during plating), and the reducing agent hypophosphite (concentration 0.1mol / L) is introduced dropwise during plating. The plating solution contains a complexing agent, citric acid, preferably at a concentration of 0.1 mol / ml. It also contains a stabilizer, lead nitrate. During the electroless plating process, the pH is controlled at 8.8–9.2 (adjusters can be conventional acids such as hydrochloric acid or nitric acid, or alkalis such as sodium hydroxide). The preferred electroless plating temperature is 80℃. After plating, conventional post-treatment methods such as water washing or acid washing can be used to remove unwanted substances from the powder. Finally, the dried coated powder is placed in a vacuum tube furnace and held at 350℃ for 60 minutes (vacuum degree 10). -3 -10 -1 Pa), vacuum sealed and stored, to obtain Composite coated diamond.

[0058] Laser additive manufacturing process: completely consistent with Example 1. The number of pitting defects per 50 square millimeters of the obtained WCo diamond composite coating is shown in Table 1, and the crack situation within the 50 square millimeter view frame is shown in Table 1.

[0059] Comparative Example 1:

[0060] WNi composite coated diamond: The preparation of the first coating layer is completely consistent with that in Example 1.

[0061] The second coating layer is made of electroplated nickel. The W-plated diamond particle sample is placed in a solution containing electroplated Ni for electroplating. The anode and cathode are composed of a nickel plate and W-plated diamond, respectively, to obtain diamond particles with a W-Ni structure coating on the surface.

[0062] The nickel plating solution consists of 350 g / L nickel sulfate, 25 g / L boric acid, 55 g / L nickel chloride, 12 ml / L formaldehyde, 0.8 g / L saccharin, and 0.6 g / L cadmium sulfate. The electroplating temperature is 30°C, and the current density is 3 A / dm³. 2 The electroplating time is 30 minutes. The electroplated product is then held at 500℃ for 60 minutes in an argon atmosphere.

[0063] Laser additive manufacturing process: completely consistent with Example 1. The number of pitting defects per 50 square millimeters of the obtained WNi diamond composite coating is shown in Table 1, and the crack situation within the 50 square millimeter view frame is shown in Table 1.

[0064] Comparative Example 2:

[0065] W-Co composite coated diamond: The preparation of the first coating layer is completely consistent with that in Example 1.

[0066] The second coating layer was applied using a sprayed fluidized bed cobalt plating process (under the same conditions as Comparative Example 1).

[0067] The second coating layer was produced using a combined spray fluidized bed granulation system. 100g of W-plated diamond and 125g of pure Co powder were weighed out. Isopropanol was used as the solvent, and polyethylene glycol and acrylic resin were selected as the dispersant and binder, respectively, at 3wt.% and 6wt.% of the Co powder. 350ml of isopropanol was weighed out, and the dispersant was added and dissolved in a water bath at 60-80℃. The Co powder was then introduced and dispersed using a stirrer to obtain a colloid. Finally, the binder was added and thoroughly stirred to form a slurry. A combined spray fluidized bed granulation system was used for coating. Finally, the dried coated powder was placed in a vacuum tube furnace and held at 950℃ for 60 minutes, then vacuum-sealed for storage.

[0068] The laser power is 1200W, the scanning speed is 7mm / s, and the diamond is... The composite coated diamond has a particle size of 90~106μm, and the metal-based alloy binder phase has a particle size of 45~150μm. It is preheated to 200℃ and contains a lot of cavitation defects in the coating.

[0069] Comparative Example 3

[0070] The other conditions are the same as in Example 1, except that: after the second coating layer is chemically plated, it is not subjected to high-temperature heat treatment, but is dried at 60 degrees Celsius for 24 hours.

[0071] The resulting product had cracks and numerous cavitation defects.

Claims

1. A method for suppressing "cavitation" defects in laser-clad diamond composite coatings, characterized in that: Includes the following steps: Step 1 Using clean and dry diamond as the processing object, diamond with tungsten or titanium coating is prepared by magnetron sputtering, denoted as material A; Step Two A second coating layer is deposited on material A by chemical plating. The material of the second coating layer is selected from at least one of Co, Ni, and Cu. After the chemical plating is completed, the material is kept at 900~980℃ for 30~90min under vacuum atmosphere to obtain a spare powder with a particle size of 95~106 μm. Step 3 The spare powder and metal bonding powder are placed in separate hoppers; the carrier gas flow rate for both the spare powder and metal bonding powder is controlled at 8-12 L / min, and laser cladding printing is performed to obtain the product. During laser cladding printing, the laser power is controlled at 1200W~1800W, the scanning speed is 7~16mm, the spot diameter is between 2.5-4mm, the carrier gas is argon, the powder feeding rate of the spare powder is 1.8~2g / min, and the powder feeding rate of the metal bonding powder is 6~8g / min.

2. The method for suppressing "cavitation" defects in laser-clad diamond composite coatings according to claim 1, characterized in that: Using clean and dry diamond as the target material, the first coating layer is prepared on the surface of the target material by magnetron sputtering. Specifically, high-purity tungsten or Ti is used as the target material, and the surface of the target material is coated at a temperature of 300-400℃. The protective atmosphere is argon, and the vacuum degree of the deposition chamber is controlled at ≤10. -1 Pa, deposition rate of 45~55nm / min; to obtain a first coating layer with a thickness of 100-200 nm; the thickness of the first coating layer is 50-200 nm, preferably 100-200 nm.

3. The method for suppressing "cavity" defects in laser-clad diamond composite coatings according to claim 1, characterized in that: In the electroless plating solution, the concentration of the raw material salt is 30-40 g / L, and the raw material salt is selected from at least one of water-soluble cobalt salt, water-soluble nickel salt, and water-soluble copper salt. The water-soluble cobalt salt is selected from at least one of cobalt chloride and cobalt nitrate; The water-soluble nickel salt is selected from at least one of nickel chloride, nickel nitrate, and nickel sulfate; The water-soluble copper salt is selected from at least one of copper sulfate and copper chloride.

4. The method for suppressing "cavity" defects in laser-clad diamond composite coatings according to claim 1, characterized in that: During electroless plating, the reducing agent solution is added to the plating solution dropwise while stirring. The concentration of the reducing agent in the solution is 20-40 g / L. Electroless plating yields a second coating with a thickness of 5-10 micrometers.

5. The method for suppressing "cavity" defects in laser-clad diamond composite coatings according to claim 4, characterized in that: The reducing agent is hypophosphoric acid and / or hypophosphite; The hypophosphite is selected from at least one of sodium hypophosphite and calcium hypophosphite.

6. The method for suppressing "cavity" defects in laser-clad diamond composite coatings according to claim 1, characterized in that: The electroless plating solution also contains a complexing agent; the complexing agent is selected from at least one of citric acid, malic acid, succinic acid, and acetic acid, and the concentration is 0.03-0.2 mol / ml.

7. The method for suppressing "cavity" defects in laser-clad diamond composite coatings according to claim 1, characterized in that: The electroless plating solution contains stabilizers; the stabilizers are lead salts or cadmium salts, and their concentration is 1-5 ppm.

8. The method for suppressing "cavitation" defects in laser-clad diamond composite coatings according to claim 1, characterized in that: The chemical plating solution has a pH value of 8-10; the chemical plating temperature is 30-90℃.

9. The method for suppressing "cavity" defects in laser-clad diamond composite coatings according to claim 1, characterized in that: After the chemical plating is completed, under a vacuum atmosphere, the temperature is first raised to 300-400℃ at a heating rate of 5-10℃ / min and held for 10-20min, and then raised to 900-980℃ and held for 30-90min.

10. The method for suppressing "cavity" defects in laser-clad diamond composite coatings according to claim 1, characterized in that: The diamond particle size after coating is 90~106 μm; The particle size range of the metal binder is 45-150 μm; the metal binder includes a high-entropy alloy; the high-entropy alloy is an FeCoCrNiAl high-entropy alloy.

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