A laser additive manufacturing method for diamond composite powder and its application

Abstract

This invention belongs to the field of laser additive manufacturing technology, specifically relating to a laser additive manufacturing diamond composite powder with low interfacial residual stress, its preparation method, and its application. The laser additive manufacturing diamond composite powder includes a diamond particle core, a first coating layer, and a second coating layer; wherein the first coating layer coats the diamond particle core, and the second coating layer coats the first coating layer, the melting point or melting temperature of the first coating layer is higher than that of the second coating layer; the second coating layer undergoes a phase transition with volume expansion upon heating, and its preparation method includes electroplating. This invention, for the first time, uses an appropriate electroplating process to prepare a Co layer, reducing the interfacial residual stress of the diamond composite material obtained through 3D printing to below 120 MPa. This invention features a reasonable structural design, a simple and controllable preparation process, and produces a product with excellent performance, facilitating industrial application.

Description

Technical Field

[0001] This invention belongs to the field of laser additive manufacturing technology, specifically relating to a laser additive manufacturing diamond composite powder with low interfacial residual stress, its preparation method, and its application. Background Technology

[0002] Despite the high hardness and wear resistance of diamond composites, the high interfacial residual stress between diamond and the matrix limits their application in harsh mechanical environments. To alleviate the interfacial stress caused by thermal cycling and the difference in thermal expansion coefficients in the LPBF process, several strategies have been proposed: (1) Optimizing LPBF process parameters, such as laser power, scanning speed, layer thickness, and scanning strategy, to reduce the stress caused by thermal cycling. However, even so, the crack control effect is still not ideal for composites that are prone to interfacial cracking. (2) Adding a second soft phase to the matrix. The second soft phase reduces thermal stress by releasing strain energy, thereby effectively suppressing the formation of microcracks during LAM. However, the second soft phase cannot completely eliminate surface cracks, and this adjustment cannot eliminate the residual stress caused by the difference in thermal expansion coefficients at the composite interface. The presence of the soft phase will reduce the overall hardness and wear resistance of the parts. (3) Constructing a transition layer with a thermal expansion coefficient between the hard phase and the binder. The transition layer, acting as a buffer layer, improves the interfacial bonding of heterogeneous materials and effectively alleviates the residual stress at the interface caused by differences in thermal expansion coefficients, thus reducing the initiation of microcracks. For example, attempts have been made to use metallic coatings, such as W, B, Ni, Zr, Cr, and Ti, to control the residual stress at the diamond abrasive grain interface, but this improvement is limited. Especially for diamond composite materials manufactured using laser additive manufacturing processes, currently developed printing materials struggle to produce diamond composite materials with low interfacial residual stress. There are some reports in existing technologies that employ composite coatings designed on the diamond surface, such as the strategy in patent CN107900327A using Cr7C3 as the inner layer and copper as the outer coating layer, but this technology does not address how to reduce the residual stress of the product. Summary of the Invention

[0003] In order to develop laser additive manufacturing diamond composite materials with low interfacial residual stress, and to address the problems of existing printing materials in the rapid heating and cooling, intense molten pool flow, laser additive manufacturing process, such as difficulty in controlling scale effects and discontinuous interfacial carbides, which make them incompatible with the rapid melting and solidification process of laser additive manufacturing, this invention is the first to attempt a strategy to reduce product residual stress by utilizing the characteristics of double-layer coating and the volume expansion caused by phase change in the outer coating layer during the printing process, and has achieved good results.

[0004] This invention discloses a laser additive manufacturing method for diamond composite powder, comprising a diamond particle core, a first coating layer, and a second coating layer; wherein the first coating layer coats the diamond particle core, the second coating layer coats the first coating layer, the melting point or melting temperature of the first coating layer is higher than that of the second coating layer, and the second coating layer undergoes a phase transition with volume expansion upon heating.

[0005] As a preferred embodiment, the present invention provides a laser additive manufacturing method for diamond composite powder, comprising at least two schemes, wherein the first scheme is: the material of the first coating layer is preferably tungsten (W) or tungsten alloy, and the material of the second coating layer is preferably electroplated cobalt (Co) or electroplated cobalt alloy.

[0006] The second option is: the material of the first coating layer is preferably tungsten (W) or tungsten alloy, and the material of the second coating layer is preferably granulated cobalt (Co) or cobalt alloy.

[0007] The third option is: the material of the first coating layer is preferably titanium (Ti) or titanium alloy, and the material of the second coating layer is preferably copper (Cu) or copper alloy.

[0008] As a further preferred embodiment, the present invention provides a laser additive manufacturing method for diamond composite powder, wherein the material of the first coating layer is preferably tungsten (W) or a tungsten alloy, and the material of the second coating layer is preferably electroplated cobalt (Co) or an electroplated cobalt alloy.

[0009] Preferably, this invention provides a laser additive manufacturing method for diamond composite powder, wherein the thickness of the first coating layer is 100-300 nanometers (preferably 150-220 nanometers), and the thickness of the second coating layer is 5-25 micrometers, preferably 7-15 micrometers. This invention controls the thickness of the first and second coating layers to effectively control the risk of internal cracking of the coating while ensuring interfacial bonding. Diamond surface coatings (such as nickel, titanium, chromium, etc.) are commonly used to improve the wettability and interfacial bonding strength between diamond and the matrix material. A coating that is too thin may not effectively prevent direct contact between the diamond surface and the matrix, resulting in insufficient interfacial bonding. An excessively thick coating may cause stress concentration or increase the risk of delamination. A coating of appropriate thickness can significantly improve interfacial bonding strength and enhance the mechanical properties of the composite material.

[0010] One preferred embodiment of the present invention is a strategy to improve the wear resistance of diamond composite materials by reducing residual stress through a double coating of tungsten (W) and cobalt (Co) on the surface of diamond particles. When the printing material designed in this invention is used to obtain the final product through laser additive manufacturing, the W layer contributes to metallurgical bonding and thermal stability, while the Co layer undergoes a phase transition from HCP to FCC upon cooling, causing volume expansion and effectively reducing residual stress.

[0011] This invention discloses a method for preparing diamond composite powder using laser additive manufacturing, comprising the following steps:

[0012] Step 1: Preparation of the first coating layer

[0013] Using the material of the first coating layer as the target, diamond is surface-coated at a temperature of 300-400 °C. The protective atmosphere is argon, and the vacuum degree of the deposition chamber is controlled to be less than or equal to 1 Pa, preferably less than or equal to 10 Pa. -1 Pa, with a deposition rate of 40-60 nm / min, preferably 50 nm / min. A first coating layer of approximately 170-195 nm thickness is formed on the surface of the diamond particles.

[0014] Step 2: Preparation of the second coating layer

[0015] A second coating layer is applied to the surface of a diamond with a first coating layer to obtain laser additive manufacturing diamond composite powder.

[0016] Preferably, the material of the first coating layer is tungsten.

[0017] Preferably, the preparation of the second coating layer includes the following steps:

[0018] The W-plated diamond particle sample was placed in a Co plating solution for electroplating. The anode and cathode were composed of a cobalt plate and W-plated diamond, respectively, to obtain diamond particles with a W-Co structure coating on the surface.

[0019] The Co electroplating solution comprises 350–500 g / L cobalt sulfate, 30–45 g / L boric acid, 45 g / L cobalt chloride, 10–15 ml / L formaldehyde, 1–1.5 g / L saccharin, and 0.4–0.5 g / L cadmium sulfate. The electroplating temperature is 30–50°C, and the current density is 2–4 A / dm³. 2 The electroplating time is 20–100 min. Laser additive manufacturing diamond composite powder is obtained and used as a spare material for laser additive manufacturing.

[0020] The resulting laser additive manufacturing diamond composite powder has a particle size of 10-200 micrometers, preferably 45-150 micrometers, more preferably 90-140 micrometers, and even more preferably 100-120 micrometers. That is, the particle size of the laser additive manufacturing feedstock is 10-200 micrometers, preferably 45-150 micrometers, more preferably 90-140 micrometers, and even more preferably 100-120 micrometers.

[0021] The present invention relates to an application of laser additive manufacturing of diamond composite powder, comprising printing a mixed powder containing the obtained laser additive manufacturing diamond composite powder into a mold by laser additive manufacturing.

[0022] The mixed powder includes a matrix powder and the resulting laser additive manufacturing diamond composite powder;

[0023] The conditions for the laser additive manufacturing process used are as follows:

[0024] When using laser cladding (LC), the preferred process is: laser power of 1200~1800W and scanning speed of 7~16mm / s.

[0025] When using selective laser melting (SLM) technology, the preferred process is: laser power of 100-300W and scanning speed of 500-1500mm / s.

[0026] This invention relates to an application of laser additive manufacturing of diamond composite materials. The preferred printing process is selective laser melting (SLM), with a laser power of 120~180W, more preferably 180W, a laser scanning speed of 700~1300mm / s, more preferably 900mm / s, a scanning spacing of 30-70μm, preferably 50μm, a layer thickness of 30-100μm, preferably 70μm, and an interlayer scanning angle of 45-90°, preferably 67°.

[0027] This invention relates to an application of laser additive manufacturing of diamond composite materials, wherein the matrix powder is selected from at least one of CuSn, Ni-based self-fluxing alloy, Fe-based self-fluxing alloy, and FeCoCrNi-based high-entropy alloy.

[0028] Principles and advantages

[0029] The principle of phase transformation-compressibility-stress relief: Fundamentally, residual stress is caused by non-uniform volume changes resulting from the presence of multiphase structures in metals, leading to non-uniform deformation. Therefore, utilizing volume changes induced by phase transformation provides a new method for residual stress relaxation. Iyota et al. studied the effect of martensitic phase transformation on residual stress in spot-welded high-strength steel plates. Their research showed that residual stress decreased near 400℃ due to the negative thermal expansion caused by martensitic phase transformation. Badrinarayanan et al. incorporated zirconium tungstate nanoparticles with negative thermal expansion properties into thermosetting polymer matrices, effectively improving the dimensional stability of the polymer matrix composites. Simultaneously, the phase transformation of Co from HCP to FCC also produces an effect similar to negative thermal expansion, introducing a functional transition layer with a "phase transformation-induced expansion" effect at the interface between diamond and the metal matrix, which can effectively reduce residual stress at the finished product interface. Furthermore, during the exploration and verification process of this invention, it was found that a Co layer prepared using an appropriate electroplating process can further reduce residual stress at the finished product interface and improve the elastic modulus of the product.

[0030] Advantages: Unlike traditional methods that reduce the overall residual stress of composite materials, this method effectively alleviates the residual stress at the interface at a distance of micrometers, significantly reducing the risk of cracking at the interface of heterogeneous materials.

[0031] This invention is the first to use an electroplating process to prepare a Co layer, which enables the residual stress at the finished product interface to be rapidly reduced to below 120 MPa. Attached Figure Description

[0032] Figure 1 This is a photograph of the tungsten-coated particles from Example 1.

[0033] Figure 2 Examples 1 and 2, and Comparative Example 1, show the nanoindentation curves and indentation location diagrams of the substrate;

[0034] Figure 3 This is a schematic diagram of W-Co coated diamond in Example 1. Detailed Implementation

[0035] Exploration Experiment

[0036] Example 1-1

[0037] The preparation process of W-Co diamond composite powder is as follows: (1) Magnetron sputtering: High-purity tungsten is used as the target material, and diamond (particle size of 90~106 micrometers) is coated on the surface at 400℃. The protective atmosphere is argon, and the vacuum degree of the deposition chamber is controlled at 10. -1 Pa, deposition rate of 50 nm / min.

[0038] CuSn10 diamond composites were prepared by rapid hot pressing sintering using diamonds with different W layer thicknesses (the mass ratio of CuSn10 matrix powder to diamonds with different W layer thicknesses was 9:1; the hot pressing process parameters were: temperature 960℃, pressure 50MPa, sintering holding time 1h, and cooling method: furnace cooling). The thermal conductivity of the composites was measured, and the experimental results are shown in Table 1.

[0039]

[0040] The results showed that the composite material exhibited the highest thermal conductivity when the W layer thickness was approximately 200 nm. For heterogeneous interfaces, better interfacial bonding resulted in higher thermal conductivity. Therefore, it was determined that a first coating W layer thickness of approximately 200 nm provided the best interfacial bonding quality and resulted in the optimal performance of the composite material.

[0041] Example 1

[0042] The preparation process of W-Co diamond composite powder is as follows: (1) Magnetron sputtering: High-purity tungsten is used as the target material, and diamond (particle size of 90~106 micrometers) is coated on the surface at 400℃. The protective atmosphere is argon, and the vacuum degree of the deposition chamber is controlled at 10. -1 Pa, deposition rate of 50 nm / min. A tungsten elemental coating with an average thickness of approximately 180-200 nm is formed on the surface of the diamond particles, such as... Figure 1 As shown.

[0043] W-plated diamond particle samples were immersed in a Co plating solution for electroplating. The anode and cathode consisted of a cobalt plate and W-plated diamond, respectively, resulting in diamond particles with a W-Co structure coating on the surface. The Co plating solution consisted of 450 g / L cobalt sulfate, 40 g / L boric acid, 45 g / L cobalt chloride, 12 ml / L formaldehyde, 1.5 g / L saccharin, and 0.5 g / L cadmium sulfate. The electroplating temperature was 40℃, and the current density was 3 A / dm³. 2 Laser additive manufacturing diamond composite powder particles with a particle size of 100~120 micrometers were obtained by electroplating Co under the conditions of 40 min (sample 1) and 60 min (sample 2).

[0044] CuSn10 matrix powder (particle size 15-53 micrometers) and laser additive manufacturing diamond composite powder are mixed uniformly (the mass ratio of CuSn10 matrix powder to laser additive manufacturing diamond composite powder is 15:1). The product is then printed using a laser additive manufacturing process, with the following conditions:

[0045] The laser power is 180 W, the laser scanning speed is 900 mm / s, the scanning spacing is 50 μm, the layer thickness is 70 μm, the interlayer scanning angle is 67°, and the printed sample is cut from the substrate parallel to the XY plane by an electrical discharge wire cutting machine.

[0046]

[0047] The residual stress on the matrix side of the interface of four composite materials was evaluated using nanoindentation. The indentation locations and nanoindentation curves for the CuSn10 / diamond composite are shown below. Figure 2 As shown in Table 2, the indentation depth, equivalent hardness, Young's modulus, stress properties, and calculated residual stress at each point are shown. The interfacial residual stress of the electroplated W-Co coated diamond composite material is significantly lower than that of the uncoated diamond, Ti-Cu coated diamond, and granulated W-Co coated diamond composite materials.

[0048]

[0049] Example 2

[0050] W-plated diamond particles were prepared according to Example 1.

[0051] Granulation: Weigh 100 g of tungsten-plated diamond (particle size 90-106 μm) and 125 g of pure Co powder (D50=1.14 μm). Use isopropanol as solvent, and polyethylene glycol and acrylic resin as dispersant and binder, respectively, at 3 wt.% and 6 wt.% of the Co powder. Weigh 350 ml of isopropanol, add the dispersant first, and dissolve it in a 60 ℃ water bath. Add the Co powder and disperse it with a stirrer to obtain a colloid. Finally, add the binder and stir thoroughly to form a slurry. Coat the W-plated diamond: Place the W-plated diamond into a coating chamber, and use an air blower to evenly agitate the diamond particles into a fluidized state. At this time, a peristaltic pump delivers the slurry from the beaker to the spray gun, and the slurry is deposited on the surface of the suspended diamond through spray atomization, thereby achieving coating.

[0052] Degreasing / Pre-sintering: The dried pre-coated powder is placed in a vacuum tube furnace and held at 950 ℃ for 60 min. Polyethylene glycol and acrylic resin undergo thermal decomposition under vacuum conditions, and the composite powder is then pre-sintered at high temperature to achieve a certain strength. The resulting laser additive manufacturing diamond composite powder has a particle size of 110-140 micrometers.

[0053] CuSn10 matrix powder (particle size 15-53 micrometers) and laser additive manufacturing diamond composite powder are mixed evenly, and then the product is printed using a laser additive manufacturing process. The conditions of the laser additive manufacturing process are as follows:

[0054] The laser power is 180 W, the laser scanning speed is 900 mm / s, the scanning spacing is 50 μm, the layer thickness is 70 μm, the interlayer scanning angle is 67°, and the printed sample is cut from the substrate parallel to the XY plane by an electrical discharge wire cutting machine.

[0055] The residual stress on the matrix side of the interface of three composite materials was evaluated using nanoindentation. The results are as follows: Figure 2 As shown in Table 2.

[0056] Example 3

[0057] The preparation process of Ti-Cu diamond composite powder is as follows: (1) Magnetron sputtering: High-purity titanium is used as the target material, and diamond is coated on the surface at 300℃. The protective atmosphere is argon, and the vacuum degree of the deposition chamber is controlled at 10. -1 Pa, deposition rate of 50 nm / min. A layer of elemental titanium about 200 nm thick is formed on the surface of diamond particles. (2) 10-15 micrometers of elemental copper is deposited on the surface of diamond by chemical plating.

[0058] Ti-Cu coated diamond was used to replace the W-Co coating layer in Example 1, and the printing conditions were exactly the same as in Example 1; the performance of the product is shown in Table 2. The results show that the interfacial residual stress of the W-Co coated diamond composite material is significantly lower than that of the uncoated diamond and Ti-Cu coated diamond composite materials.

[0059] Comparative Example 1

[0060] The W-Co coated diamond in Example 1 was replaced with bare diamond, and the printing conditions were exactly the same as in Example 1; the performance of the product is shown in Table 2.

Claims

1. A method for preparing diamond composite powder by laser additive manufacturing, characterized in that: The laser additive manufacturing diamond composite powder includes a diamond particle core, a first coating layer, and a second coating layer; wherein, the first coating layer coats the diamond particle core, the second coating layer coats the first coating layer, the melting point or melting temperature of the first coating layer is higher than that of the second coating layer, and the second coating layer expands in volume when heated; In the laser additive manufacturing diamond composite powder, the first coating layer is made of tungsten or a tungsten alloy, and the second coating layer is made of electroplated cobalt or an electroplated cobalt alloy. The preparation method includes the following steps: Step 1: Preparation of the first coating layer Using the material of the first coating layer as the target, diamond particles are surface coated at a temperature of 300-400 ℃. The protective atmosphere is argon, the vacuum degree of the deposition chamber is controlled to be less than or equal to 1 Pa, and the deposition rate is 40~60 nm / min. Step 2: Preparation of the second coating layer The W-plated diamond particle sample was placed in an electroplating tank containing a Co plating solution for electroplating. The anode and cathode were composed of a cobalt plate and W-plated diamond, respectively, to obtain diamond particles with a W-Co structure coating on the surface. The Co electroplating solution comprises 350–500 g / L cobalt sulfate, 30–45 g / L boric acid, 45 g / L cobalt chloride, 10–15 ml / L formaldehyde, 1–1.5 g / L saccharin, and 0.4–0.5 g / L cadmium sulfate. The electroplating temperature is 30–50°C, and the current density is 2–4 A / dm³. 2 The electroplating time is 20 to 100 minutes.

2. The method for preparing laser additive manufacturing diamond composite powder according to claim 1, characterized in that: The thickness of the first coating layer is 100-300 nanometers, and the thickness of the second coating layer is 5-25 micrometers.

3. The method for preparing laser additive manufacturing diamond composite powder according to claim 1, characterized in that: The first coating layer is made of tungsten.

4. The method for preparing laser additive manufacturing diamond composite powder according to claim 1, characterized in that: The resulting laser additive manufacturing diamond composite powder has a particle size of 10-200 micrometers.

5. An application of the laser additive manufacturing diamond composite powder prepared according to any one of claims 1-4, characterized in that: The mixed powder containing the obtained laser additive diamond composite powder is printed into shape using laser additive manufacturing. The mixed powder includes a matrix powder and the resulting laser additive manufacturing diamond composite powder; The conditions for the laser additive manufacturing process used are as follows: When using laser cladding, the process parameters are: laser power 1200~1800W, scanning speed 7~16mm / s; When selective laser melting is used, the process parameters are: laser power of 100-300W and scanning speed of 500-1500mm / s.

6. The application according to claim 5, characterized in that: The printing process is selective laser melting, with a laser power of 120~180W, a laser scanning speed of 700~1300mm / s, a scanning spacing of 30-70μm, a layer thickness of 30-100μm, and an interlayer scanning angle of 45-90°. The matrix powder used is selected from at least one of CuSn, Ni-based self-fluxing alloy, Fe-based self-fluxing alloy and FeCoCrNi-based high-entropy alloy.

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