A method for preparing diamond coating by laser cladding

Abstract

The present invention relates to the field of coating technology, and specifically to a method for preparing a diamond coating by laser cladding. First, the surface of the substrate is polished and cleaned, and then a gradient transition layer is prepared on the surface of the substrate. A laser cladding powder material is obtained by mixing pre-coated diamond, alloy powder and rare earth oxide. Under the protection of an inert gas, the laser cladding powder material is cladded on the gradient transition layer to form a diamond coating. Subsequently, the diamond coating is annealed. The diamond coating prepared by the present invention has excellent mechanical properties and bonding strength.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and specifically to a method for preparing a diamond coating by laser cladding. Background Art

[0002] The diamond coating on the surface of cemented carbide can significantly improve the service life of tools and machine tool parts, improve the surface roughness of machining and enhance the machining quality. However, due to the insufficient bonding force between the diamond coating and the cemented carbide, it restricts its further expansion in the machining field. How to improve the mechanical properties of the diamond coating, improve its bonding strength with the cemented carbide, and extend its service life has become the current research focus. Summary of the Invention

[0003] Object of the Invention: Aiming at the above technical problems, the present invention proposes a method for preparing a diamond coating by laser cladding.

[0004] The technical solution adopted is as follows:

[0005] A method for preparing a diamond coating by laser cladding, comprising the following steps:

[0006] S1: Polish and clean the surface of the substrate;

[0007] S2: Prepare a gradient transition layer on the surface of the substrate, and the gradient transition layer sequentially includes a first transition layer containing metal carbide and a second transition layer containing metal carbide and metal nitride;

[0008] S3: Disperse diamond nano-powder in a solvent, then add 1-butyl-3-vinylimidazolium tetrafluoroborate, divinylbenzene and a radical initiator, heat up for reaction, then return to room temperature, collect the precipitate and dry it under vacuum to obtain pre-coated diamond;

[0009] S4: Mix the pre-coated diamond, alloy powder and rare earth oxide to obtain a laser cladding powder;

[0010] S5: Use a coaxial powder feeding laser cladding device to cladding the laser cladding powder on the gradient transition layer under the protection of inert gas to form a diamond coating;

[0011] S6: Subsequently, perform annealing treatment on the diamond coating, the annealing temperature is 600 - 900 °C, and the annealing time is 60 - 180 min.

[0012] Further, the substrate is YG8 cemented carbide.

[0013] Further, the first transition layer is composed of titanium carbide, tungsten carbide and titanium metal with a mass ratio of 1 - 5:1 - 5:1 - 5.

[0014] Further, the second transition layer is composed of titanium carbide, tungsten carbide, titanium nitride, chromium nitride, and titanium metal with a mass ratio of 1-5:1-5:1-5:1-5:1-5.

[0015] Further, the molar ratio of the 1-butyl-3-vinylimidazolium tetrafluoroborate to divinylbenzene is 1-10:1.

[0016] Further, in S3, the solvent is composed of absolute ethanol, deionized water, and acetonitrile; the temperature-rising reaction is to raise the temperature to 70-75°C and react for 12-48 h.

[0017] Further, the mass ratio of the pre-coated diamond, alloy powder, and rare earth oxide is 1-4:5-10:0.1-0.3.

[0018] Further, the alloy powder is 718 nickel alloy powder.

[0019] Further, the rare earth oxide is lanthanum oxide and / or cerium oxide.

[0020] Further, in S5, the laser power is 1000-3000 W, the spot diameter is 5-10 mm, the powder feeding rate is 10-50 g / min, and the scanning speed is 180-300 mm / min.

[0021] Advantages of the present invention:

[0022] The present invention provides a method for preparing a diamond coating by laser cladding. The prepared diamond coating has excellent mechanical properties and bonding strength, and can effectively extend the service life of the cemented carbide substrate;

[0023] Combined treatment of polishing and cleaning the substrate can form a micron-level roughness on the substrate surface, increase the mechanical bite area of the gradient transition layer, improve the bite strength, and through the gradient transition layer, the thermal expansion coefficient and chemical compatibility between the substrate and the diamond coating can be gradually matched, reduce the interface stress, avoid the peeling of the diamond coating, and extend the service life;

[0024] By coating diamond nanopowders with polyionic liquid, on the one hand, the burning loss of diamond during the cladding process is reduced, and the graphitization of diamond is inhibited. On the other hand, the active boron atoms and carbon atoms generated by the pyrolysis of polyionic liquid during laser cladding can react with the alloy powder to form corresponding borides and carbides, improve the wettability between diamond and the metal melt, and fill the interface gap, thus enhancing the bonding strength;

[0025] Adding rare earth oxides can significantly improve the distribution of diamond in the molten pool, avoid segregation caused by density differences. At the same time, rare earth elements can promote interfacial reactions, enhancing the bonding strength of the diamond coating. Annealing can eliminate residual stress, significantly change the microstructure of the diamond coating, stabilize the size, reduce the tendency of deformation and crack, and eliminate tissue defects, which all play a positive role in improving the mechanical properties and bonding strength of the diamond coating. Detailed implementation mode

[0026] For those not specifying specific conditions in the examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments not indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase. Technologies not mentioned in the present invention refer to the prior art. Unless otherwise specified, the following examples and comparative examples are parallel tests and adopt the same treatment steps and parameters.

[0027] Example 1:

[0028] A method for preparing a diamond coating by laser cladding, comprising the following steps:

[0029] S1: Using YG8 cemented carbide as the substrate, polishing the substrate to make its surface roughness 4.5 μm, then successively ultrasonic cleaning it with acetone and absolute ethanol, and then drying the surface with a hot air blower;

[0030] S2: Preparing a gradient transition layer on the surface of the substrate. The gradient transition layer successively includes a first transition layer with a thickness of 250 μm and a second transition layer with a thickness of 100 μm. When preparing the first transition layer, titanium carbide, tungsten carbide and titanium metal powder with a mass ratio of 1:1:2 are used as raw materials. After fully ball milling them, under argon gas protection, a coaxial powder feeding laser cladding device is used to laser clad the raw materials on the surface of the substrate to form the first transition layer. The laser power is 2000 W, the spot diameter is 5 mm, the powder feeding rate is 20 g / min, and the scanning speed is 200 mm / min. When preparing the second transition layer, titanium carbide, tungsten carbide, titanium nitride, chromium nitride and titanium metal powder with a mass ratio of 1:1:1:1:4 are used as raw materials. After fully ball milling them, under argon gas protection, a coaxial powder feeding laser cladding device is used to laser clad the raw materials on the surface of the first transition layer to form the second transition layer. The laser power is 2000 W, the spot diameter is 5 mm, the powder feeding rate is 20 g / min, and the scanning speed is 200 mm / min;

[0031] S3: 1g of diamond nanopowder was dispersed in a mixed solvent consisting of 10ml of anhydrous ethanol, 10ml of deionized water and 20ml of acetonitrile, and then 10mmol of 1-butyl-3-vinyl imidazole tetrafluoroborate, 5mmol of divinylbenzene and 5mmol of azobisisobutyronitrile were added. The temperature was raised to 75℃ for reaction for 24h and then returned to room temperature. The precipitate was collected, washed with anhydrous ethanol and then dried in a vacuum to obtain pre-coated diamond. The pre-coated diamond, inconel 718 nickel alloy powder and lanthanum oxide with a mass ratio of 3:7:0.2 were fully ball-milled to obtain laser cladding powder. The coaxial powder feeding laser cladding equipment was used to clad the laser cladding powder on the second transition layer under argon protection to form a diamond coating with a thickness of 120μm. The laser power was 3000W, the spot diameter was 5mm, the powder feeding rate was 10g / min, and the scanning speed was 200mm / min. min, and then the diamond coating was annealed at a temperature of 800°C for 80 min.

[0032] Embodiment 2:

[0033] The method is substantially the same as Example 1, except that cerium oxide is used instead of lanthanum oxide;

[0034] A method for preparing a diamond coating by laser cladding comprises the following steps:

[0035] S1: YG8 cemented carbide was used as the substrate, and the substrate was polished to a surface roughness of 4.5 μm. Then, it was ultrasonically cleaned with acetone and anhydrous ethanol in sequence, and the surface was dried with a hot air blower;

[0036] S2: A gradient transition layer is prepared on the surface of the substrate, and the gradient transition layer includes a first transition layer with a thickness of 250 μm and a second transition layer with a thickness of 100 μm. When preparing the first transition layer, titanium carbide, tungsten carbide and metal titanium powder with a mass ratio of 1:1:2 are used as raw materials. After being fully ball-milled, coaxial powder feeding laser cladding equipment is used to laser-clad the raw materials on the surface of the substrate under the protection of argon gas to form the first transition layer. The laser power is 2000 W, the spot diameter is 5 mm, the powder feeding rate is 20 g / min, and the scanning speed is 200 mm / min. When preparing the second transition layer, titanium carbide, tungsten carbide, titanium nitride, chromium nitride and metal titanium powder with a mass ratio of 1:1:1:1:4 are used as raw materials. After being fully ball-milled, coaxial powder feeding laser cladding equipment is used to laser-clad the raw materials on the surface of the first transition layer under the protection of argon gas to form the second transition layer. The laser power is 2000 W, the spot diameter is 5 mm, the powder feeding rate is 20 g / min, and the scanning speed is 200 mm / min;

[0037] S3: 1g of diamond nanopowder was dispersed in a mixed solvent consisting of 10ml of anhydrous ethanol, 10ml of deionized water and 20ml of acetonitrile, and then 10mmol of 1-butyl-3-vinyl imidazole tetrafluoroborate, 5mmol of divinylbenzene and 5mmol of azobisisobutyronitrile were added. The temperature was raised to 75℃ for reaction for 24h and then returned to room temperature. The precipitate was collected, washed with anhydrous ethanol and then dried in a vacuum to obtain pre-coated diamond. The pre-coated diamond, inconel 718 nickel alloy powder and cerium oxide with a mass ratio of 3:7:0.2 were fully ball-milled and mixed to obtain laser cladding powder. The laser cladding powder was clad on the second transition layer under argon protection using a coaxial powder feeding laser cladding equipment to form a diamond coating with a thickness of 120μm. The laser power was 3000W, the spot diameter was 5mm, the powder feeding rate was 10g / min, and the scanning speed was 200mm / min. min, and then the diamond coating was annealed at a temperature of 800°C for 80 min.

[0038] Embodiment 3:

[0039] The method is basically the same as Example 1, except that the mass ratio of the pre-coated diamond, inconel 718 nickel alloy powder and lanthanum oxide is adjusted to 3:7:0.1;

[0040] A method for preparing a diamond coating by laser cladding comprises the following steps:

[0041] S1: YG8 cemented carbide was used as the substrate, and the substrate was polished to a surface roughness of 4.5 μm. Then, it was ultrasonically cleaned with acetone and anhydrous ethanol in sequence, and the surface was dried with a hot air blower;

[0042] S2: A gradient transition layer is prepared on the surface of the substrate, and the gradient transition layer includes a first transition layer with a thickness of 250 μm and a second transition layer with a thickness of 100 μm. When preparing the first transition layer, titanium carbide, tungsten carbide and metal titanium powder with a mass ratio of 1:1:2 are used as raw materials. After being fully ball-milled, coaxial powder feeding laser cladding equipment is used to laser-clad the raw materials on the surface of the substrate under the protection of argon gas to form the first transition layer. The laser power is 2000 W, the spot diameter is 5 mm, the powder feeding rate is 20 g / min, and the scanning speed is 200 mm / min. When preparing the second transition layer, titanium carbide, tungsten carbide, titanium nitride, chromium nitride and metal titanium powder with a mass ratio of 1:1:1:1:4 are used as raw materials. After being fully ball-milled, coaxial powder feeding laser cladding equipment is used to laser-clad the raw materials on the surface of the first transition layer under the protection of argon gas to form the second transition layer. The laser power is 2000 W, the spot diameter is 5 mm, the powder feeding rate is 20 g / min, and the scanning speed is 200 mm / min;

[0043] S3: 1g of diamond nanopowder was dispersed in a mixed solvent consisting of 10ml of anhydrous ethanol, 10ml of deionized water and 20ml of acetonitrile, and then 10mmol of 1-butyl-3-vinyl imidazole tetrafluoroborate, 5mmol of divinylbenzene and 5mmol of azobisisobutyronitrile were added. The temperature was raised to 75℃ for reaction for 24h and then returned to room temperature. The precipitate was collected, washed with anhydrous ethanol and vacuum dried to obtain pre-coated diamond. The pre-coated diamond, inconel 718 nickel alloy powder and lanthanum oxide with a mass ratio of 3:7:0.1 were fully ball-milled and mixed to obtain laser cladding powder. The coaxial powder feeding laser cladding equipment was used to clad the laser cladding powder on the second transition layer under argon protection to form a diamond coating with a thickness of 120μm. The laser power was 3000W, the spot diameter was 5mm, the powder feeding rate was 10g / min, and the scanning speed was 200mm / min. min, and then the diamond coating was annealed at a temperature of 800°C for 80 min.

[0044] Embodiment 4:

[0045] The method is basically the same as Example 1, except that the mass ratio of the pre-coated diamond, inconel 718 nickel alloy powder and lanthanum oxide is adjusted to 3:7:0.3;

[0046] A method for preparing a diamond coating by laser cladding comprises the following steps:

[0047] S1: YG8 cemented carbide was used as the substrate, and the substrate was polished to a surface roughness of 4.5 μm. Then, it was ultrasonically cleaned with acetone and anhydrous ethanol in sequence, and the surface was dried with a hot air blower;

[0048] S2: A gradient transition layer is prepared on the surface of the substrate, and the gradient transition layer includes a first transition layer with a thickness of 250 μm and a second transition layer with a thickness of 100 μm. When preparing the first transition layer, titanium carbide, tungsten carbide and metal titanium powder with a mass ratio of 1:1:2 are used as raw materials. After being fully ball-milled, coaxial powder feeding laser cladding equipment is used to laser-clad the raw materials on the surface of the substrate under the protection of argon gas to form the first transition layer. The laser power is 2000 W, the spot diameter is 5 mm, the powder feeding rate is 20 g / min, and the scanning speed is 200 mm / min. When preparing the second transition layer, titanium carbide, tungsten carbide, titanium nitride, chromium nitride and metal titanium powder with a mass ratio of 1:1:1:1:4 are used as raw materials. After being fully ball-milled, coaxial powder feeding laser cladding equipment is used to laser-clad the raw materials on the surface of the first transition layer under the protection of argon gas to form the second transition layer. The laser power is 2000 W, the spot diameter is 5 mm, the powder feeding rate is 20 g / min, and the scanning speed is 200 mm / min;

[0049] S3: Disperse 1 g of diamond nanopowder in a mixed solvent composed of 10 ml of absolute ethanol, 10 ml of deionized water, and 20 ml of acetonitrile. Then add 10 mmol of 1-butyl-3-vinylimidazolium tetrafluoroborate, 5 mmol of divinylbenzene, and 5 mmol of azobisisobutyronitrile. Heat the mixture to 75 °C and react for 24 h, then cool it to room temperature. Collect the precipitate, wash it with absolute ethanol, and then dry it under vacuum to obtain pre-coated diamond. Mix the pre-coated diamond, inconel 718 nickel alloy powder, and lanthanum oxide with a mass ratio of 3:7:0.3 by ball milling to obtain the laser cladding powder. Using a coaxial powder feeding laser cladding equipment, under the protection of argon gas, melt the laser cladding powder on the second transition layer to form a diamond coating with a thickness of 120 μm. The laser power is 3000 W, the spot diameter is 5 mm, the powder feeding rate is 10 g / min, and the scanning speed is 200 mm / min. Subsequently, anneal the diamond coating, with the annealing temperature being 800 °C and the annealing time being 80 min.

[0050] Comparative Example 1:

[0051] It is basically the same as Example 1, except that there is no gradient transition layer.

[0052] A method for preparing a diamond coating by laser cladding, comprising the following steps:

[0053] S1: Use YG8 cemented carbide as the substrate, polish the substrate to make its surface roughness 4.5 μm, then ultrasonically clean it with acetone and absolute ethanol in sequence, and then dry the surface with a hot air blower.

[0054] S2: Disperse 1 g of diamond nanopowder in a mixed solvent composed of 10 ml of absolute ethanol, 10 ml of deionized water, and 20 ml of acetonitrile. Then add 10 mmol of 1-butyl-3-vinylimidazolium tetrafluoroborate, 5 mmol of divinylbenzene, and 5 mmol of azobisisobutyronitrile. Heat the mixture to 75 °C and react for 24 h, then cool it to room temperature. Collect the precipitate, wash it with absolute ethanol, and then dry it under vacuum to obtain pre-coated diamond. Mix the pre-coated diamond, inconel 718 nickel alloy powder, and lanthanum oxide with a mass ratio of 3:7:0.2 by ball milling to obtain the laser cladding powder. Using a coaxial powder feeding laser cladding equipment, under the protection of argon gas, melt the laser cladding powder on the second transition layer to form a diamond coating with a thickness of 120 μm. The laser power is 3000 W, the spot diameter is 5 mm, the powder feeding rate is 10 g / min, and the scanning speed is 200 mm / min. Subsequently, anneal the diamond coating, with the annealing temperature being 800 °C and the annealing time being 80 min.

[0055] Comparative Example 2:

[0056] Basically the same as Example 1, except that the diamond nano-powder is not pre-coated;

[0057] A method for preparing a diamond coating by laser cladding, comprising the following steps:

[0058] S1: Using YG8 cemented carbide as the substrate, polishing the substrate to make its surface roughness 4.5 μm, then successively ultrasonically cleaning it with acetone and absolute ethanol, and then drying the surface with a hot air blower;

[0059] S2: Preparing a gradient transition layer on the surface of the substrate. The gradient transition layer successively includes a first transition layer with a thickness of 250 μm and a second transition layer with a thickness of 100 μm. When preparing the first transition layer, titanium carbide, tungsten carbide and titanium metal powder with a mass ratio of 1:1:2 are used as raw materials. After fully ball-milling them, under argon gas protection, a coaxial powder feeding laser cladding device is used to laser-clad the raw materials on the surface of the substrate to form the first transition layer. The laser power is 2000 W, the spot diameter is 5 mm, the powder feeding rate is 20 g / min, and the scanning speed is 200 mm / min. When preparing the second transition layer, titanium carbide, tungsten carbide, titanium nitride, chromium nitride and titanium metal powder with a mass ratio of 1:1:1:1:4 are used as raw materials. After fully ball-milling them, under argon gas protection, a coaxial powder feeding laser cladding device is used to laser-clad the raw materials on the surface of the first transition layer to form the second transition layer. The laser power is 2000 W, the spot diameter is 5 mm, the powder feeding rate is 20 g / min, and the scanning speed is 200 mm / min;

[0060] S3: Mixing diamond nano-powder, inconel 718 nickel alloy powder and lanthanum oxide with a mass ratio of 3:7:0.2 fully by ball-milling to obtain laser cladding powder. Using a coaxial powder feeding laser cladding device, under argon protection, the laser cladding powder is cladded on the second transition layer to form a diamond coating with a thickness of 120 μm. The laser power is 3000 W, the spot diameter is 5 mm, the powder feeding rate is 10 g / min, and the scanning speed is 200 mm / min. Subsequently, the diamond coating is annealed, the annealing temperature is 800 °C, and the annealing time is 80 min.

[0061] Comparative Example 3:

[0062] Basically the same as Example 1, except that lanthanum oxide is not included;

[0063] A method for preparing a diamond coating by laser cladding, comprising the following steps:

[0064] S1: Using YG8 cemented carbide as the substrate, polishing the substrate to make its surface roughness 4.5 μm, then successively ultrasonically cleaning it with acetone and absolute ethanol, and then drying the surface with a hot air blower;

[0065] S2: Prepare a gradient transition layer on the surface of the substrate. The gradient transition layer successively includes a first transition layer with a thickness of 250 μm and a second transition layer with a thickness of 100 μm. When preparing the first transition layer, titanium carbide, tungsten carbide, and titanium powder with a mass ratio of 1:1:2 are used as raw materials. After fully ball-milling them, under the protection of argon gas, a coaxial powder feeding laser cladding device is used to laser-clad the raw materials on the surface of the substrate to form the first transition layer. The laser power is 2000 W, the spot diameter is 5 mm, the powder feeding rate is 20 g / min, and the scanning speed is 200 mm / min. When preparing the second transition layer, titanium carbide, tungsten carbide, titanium nitride, chromium nitride, and titanium powder with a mass ratio of 1:1:1:1:4 are used as raw materials. After fully ball-milling them, under the protection of argon gas, a coaxial powder feeding laser cladding device is used to laser-clad the raw materials on the surface of the first transition layer to form the second transition layer. The laser power is 2000 W, the spot diameter is 5 mm, the powder feeding rate is 20 g / min, and the scanning speed is 200 mm / min;

[0066] S3: Disperse 1 g of diamond nanometer micropowder in a mixed solvent composed of 10 ml of absolute ethanol, 10 ml of deionized water, and 20 ml of acetonitrile. Then add 10 mmol of 1-butyl-3-vinylimidazole tetrafluoroborate, 5 mmol of divinylbenzene, and 5 mmol of azobisisobutyronitrile. Heat up to 75 °C and react for 24 h, then cool back to room temperature. Collect the precipitate, wash it with absolute ethanol, and then dry it under vacuum to obtain pre-coated diamond. Mix the pre-coated diamond and inconel 718 nickel alloy powder with a mass ratio of 3:7 by fully ball-milling to obtain laser cladding powder. Using a coaxial powder feeding laser cladding device, under the protection of argon gas, the laser cladding powder is cladded on the second transition layer to form a diamond coating with a thickness of 120 μm. The laser power is 3000 W, the spot diameter is 5 mm, the powder feeding rate is 10 g / min, and the scanning speed is 200 mm / min. Subsequently, anneal the diamond coating. The annealing temperature is 800 °C and the annealing time is 80 min.

[0067] Comparative Example 4:

[0068] Basically the same as Example 1, the difference is that no annealing treatment is carried out;

[0069] A method for preparing a diamond coating by laser cladding, comprising the following steps:

[0070] S1: Use YG8 cemented carbide as the substrate, polish the substrate to make its surface roughness 4.5 μm, then ultrasonically clean it successively with acetone and absolute ethanol, and then dry the surface with a hot air blower;

[0071] S2: Prepare a gradient transition layer on the surface of the substrate. The gradient transition layer sequentially includes a first transition layer with a thickness of 250 μm and a second transition layer with a thickness of 100 μm. When preparing the first transition layer, titanium carbide, tungsten carbide, and titanium powder with a mass ratio of 1:1:2 are used as raw materials. After fully ball-milling them, under the protection of argon gas, a coaxial powder feeding laser cladding device is used to laser-clad the raw materials on the surface of the substrate to form the first transition layer. The laser power is 2000 W, the spot diameter is 5 mm, the powder feeding rate is 20 g / min, and the scanning speed is 200 mm / min. When preparing the second transition layer, titanium carbide, tungsten carbide, titanium nitride, chromium nitride, and titanium powder with a mass ratio of 1:1:1:1:4 are used as raw materials. After fully ball-milling them, under the protection of argon gas, a coaxial powder feeding laser cladding device is used to laser-clad the raw materials on the surface of the first transition layer to form the second transition layer. The laser power is 2000 W, the spot diameter is 5 mm, the powder feeding rate is 20 g / min, and the scanning speed is 200 mm / min;

[0072] S3: Disperse 1 g of diamond nanometer micropowder in a mixed solvent composed of 10 ml of absolute ethanol, 10 ml of deionized water, and 20 ml of acetonitrile. Then add 10 mmol of 1-butyl-3-vinylimidazolium tetrafluoroborate, 5 mmol of divinylbenzene, and 5 mmol of azobisisobutyronitrile. Heat it to 75 °C and react for 24 h, then return to room temperature. Collect the precipitate, wash it with absolute ethanol, and then dry it in vacuum to obtain pre-coated diamond. Mix the pre-coated diamond, inconel 718 nickel alloy powder, and lanthanum oxide with a mass ratio of 3:7:0.2 by fully ball-milling to obtain laser cladding powder. Using a coaxial powder feeding laser cladding device, under the protection of argon gas, the laser cladding powder is cladded on the second transition layer to form a diamond coating with a thickness of 120 μm. The laser power is 3000 W, the spot diameter is 5 mm, the powder feeding rate is 10 g / min, and the scanning speed is 200 mm / min.

[0073] Performance test:

[0074] Conduct relevant performance tests on the specimens prepared in Examples 1-4 and Comparative Examples 1-4;

[0075] Use a 600MRD-S Rockwell hardness tester to measure the microhardness of the diamond coating on the surface of the specimen;

[0076] Use a UMT friction and wear tester from BRUKER Company in Germany to conduct a friction test on the diamond coating (reciprocating friction and wear, the contact method is plane, the grinding ball is a silicon nitride ball with a diameter of Φ 7.938 mm, the load is 120 N, the time is 30 min, and the reciprocating rate of the steel ball is 10 mm / s).

[0077] The Rockwell indentation method was selected for evaluation in combination with performance. A Rockwell indentation was made on the diamond coating using a 671 HRS-150 digital Rockwell hardness tester from Laizhou Huayin Testing Instrument Co., Ltd., and the indentation was observed under a microscope. The included angle of the diamond indenter tip used was 120°±20′, the applied load was 1470 N, and the loading time was 10 s.

[0078] The results of the above tests are shown in Table 1 below:

[0079] Table 1:

[0080]

[0081] Note: The VDI 3198-1992 standard classifies the coating adhesion into four grades: HF1, HF2, HF3, and HF4, where HF1 has the strongest adhesion and HF4 has the weakest adhesion;

[0082] From the comparison of Examples 1, 3 - 4 in Table 1 above, it can be seen that different addition amounts of lanthanum oxide will affect the mechanical properties of the diamond coating;

[0083] From the comparison of Examples 1 and 2 in Table 1 above, it can be seen that replacing lanthanum oxide with cerium oxide will deteriorate the mechanical properties of the diamond coating;

[0084] From the comparison of Examples 1 and Comparative Example 1 in Table 1 above, it can be seen that the setting of the gradient transition layer can greatly improve the bonding strength of the diamond coating;

[0085] From the comparison of Examples 1 and Comparative Example 2 in Table 1 above, it can be seen that the pre - coating treatment of diamond nano - micropowder plays a positive role in improving the mechanical properties of the diamond coating;

[0086] From the comparison of Examples 1 and Comparative Example 3 in Table 1 above, it can be seen that the addition of lanthanum oxide plays a positive role in improving the mechanical properties of the diamond coating;

[0087] From the comparison of Examples 1 and Comparative Example 4 in Table 1 above, it can be seen that the annealing treatment plays a positive role in improving the mechanical properties of the diamond coating.

[0088] The above examples are only used to illustrate the technical solutions of the present invention, not to limit it; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a diamond coating by laser cladding, characterized in that: The following steps are involved: S1: polishing and cleaning the surface of the substrate; S2: preparing a gradient transition layer on the surface of the substrate, wherein the gradient transition layer sequentially comprises a first transition layer containing metal carbides and a second transition layer containing metal carbides and metal nitrides; S3: dispersing diamond nanopowder in a solvent, adding 1-butyl-3-vinylimidazole tetrafluoroborate, divinylbenzene and a free radical initiator, heating the reaction, returning to room temperature, collecting the precipitate and vacuum drying to obtain a pre-coated diamond; S4: mixing the pre-coated diamond, alloy powder and rare earth oxide to obtain laser cladding powder; S5: using a coaxial powder feeding laser cladding device to clad the laser cladding powder on the gradient transition layer under the protection of an inert gas to form a diamond coating; S6: The diamond coating is then annealed at a temperature of 600-900° C. for a time of 60-180 min.

2. The method for preparing a diamond coating by laser cladding according to claim 1, characterized in that: The substrate is YG8 cemented carbide.

3. The method for preparing a diamond coating by laser cladding according to claim 1, characterized in that: The first transition layer is composed of titanium carbide, tungsten carbide and metallic titanium in a mass ratio of 1-5:1-5:1-5.

4. The method for preparing a diamond coating by laser cladding according to claim 1, characterized in that: The second transition layer is composed of titanium carbide, tungsten carbide, titanium nitride, chromium nitride and metallic titanium in a mass ratio of 1-5:1-5:1-5:1-5:1-5.

5. The method for preparing a diamond coating by laser cladding according to claim 1, characterized in that: The molar ratio of 1-butyl-3-vinylimidazole tetrafluoroborate to divinylbenzene is 1-10:

1.

6. The method for preparing a diamond coating by laser cladding according to claim 1, characterized in that: In S3, the solvent consists of anhydrous ethanol, deionized water and acetonitrile; the temperature-raising reaction is to raise the temperature to 70-75° C. and react for 12-48 hours.

7. The method for preparing a diamond coating by laser cladding according to claim 1, characterized in that: The mass ratio of the pre-coated diamond, alloy powder and rare earth oxide is 1-4:5-10:0.1-0.

3.

8. The method for preparing a diamond coating by laser cladding according to claim 7, characterized in that: The alloy powder is 718 nickel alloy powder.

9. The method for preparing a diamond coating by laser cladding according to claim 7, characterized in that: The rare earth oxide is lanthanum oxide and / or cerium oxide.

10. The method for preparing a diamond coating by laser cladding according to claim 1, characterized in that: In S5, the laser power is 1000-3000W, the spot diameter is 5-10mm, the powder feeding rate is 10-50g / min, and the scanning speed is 180-300mm / min.

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