Laser additive manufacturing double-layer structure gradient hard alloy cutter and manufacturing method

Abstract

The invention discloses a laser additive manufacturing double-layer structure gradient hard alloy cutter and a manufacturing method, the alloy cutter comprises a base body, a transition layer and a surface layer, and the transition layer is arranged between the base body and the surface layer; the base body and the transition layer are both made of WC-Co particles, and the surface layer is made of WC-TiC-TaC-Co particles; the grains of the substrate and the surface layer are smaller than those of the transition layer. The manufacturing method comprises the following steps that spherical hard alloy particles are obtained through an atomization pre-sintering granulation method; technological parameters and environmental parameters of selective laser melting are optimized; the substrate, the transition layer and the surface layer are sequentially formed through selective laser melting printing; and the double-layer structure gradient hard alloy cutter is obtained. By optimizing the atomization pre-sintering granulation method and the laser additive manufacturing process, the high-density, high-precision and high-performance gradient hard alloy cutter with the double-layer structure can be prepared.

Description

Technical Field

[0001] The present invention relates to cemented carbide cutting tools and a manufacturing method thereof, and particularly to a laser additive manufacturing double-layer structure gradient cemented carbide cutting tool and a manufacturing method thereof. Background Art

[0002] Cemented carbide has a series of excellent properties such as high hardness, high strength, high wear resistance, and low thermal expansion coefficient, and is widely used in fields such as metal processing, mining, and oil exploration, and is known as the "teeth of industry". In the past 30 years, new sintering technologies have been continuously applied to the production of cemented carbide, such as carburizing sintering method, nitriding sintering method, isostatic pressing sintering method, microwave sintering method, and spark plasma sintering method, etc.

[0003] Traditional powder metallurgy is the main method for preparing cemented carbide cutting tools, including preparation processes such as powder mixing - ball milling - forming - sintering, and the traditional forming methods of cemented carbide cutting tools include dry pressing forming, injection molding, slip casting molding, isostatic pressing molding, etc. These forming processes all completely rely on molds and have great limitations on the geometric shape design of cemented carbide cutting tools, and it is impossible to prepare cemented carbide cutting tools with complex shapes and internal structural features. Therefore, it greatly restricts the expansion of the application fields of cemented carbide. Therefore, there is an urgent need for a fast cemented carbide forming technology.

[0004] Additive manufacturing technology (3D printing) can achieve the rapid forming of cemented carbide cutting tools and realize the integration of forming and sintering. The entire manufacturing process does not require a mold, significantly shortening the R & D cycle, and is suitable for the R & D of cemented carbide cutting tool products, complex-shaped key components, personalized components, and single-piece and small-batch production. This is a technology that can directly convert the cutting tool CAD data file into a solid model and has made rapid progress in the field of intelligent manufacturing in recent years. Additive manufacturing technology has obvious advantages in breaking through the shortcomings of traditional cemented carbide manufacturing technology. Introducing additive manufacturing technology into the field of cemented carbide can theoretically completely achieve moldless manufacturing and complex part manufacturing, and can prepare functionally gradient cemented carbide by means of "printing" different materials at different parts. There is a contradictory relationship between the wear resistance and fracture toughness of traditional homogeneous structure cemented carbide, and it is difficult to improve both simultaneously. The limitation of this microstructure - macroscopic property of traditional cemented carbide severely restricts its application range in the cutting of high-hardness and difficult-to-machine materials. Gradient structure cemented carbide provides an effective way to solve the contradiction that the wear resistance and fracture toughness of traditional cemented carbide cannot be improved simultaneously. Summary of the Invention

[0005] The object of the present invention is to overcome the above-mentioned existing problems, and provide a laser additive manufacturing double-layer structured gradient cemented carbide tool and a manufacturing method thereof. By optimizing the atomization pre-sintering granulation method and the laser additive manufacturing process, the preparation of a double-layer structured gradient cemented carbide tool with high density, high precision and high performance can be realized.

[0006] The object of the present invention is achieved by the following technical solutions:

[0007] A laser additive manufacturing double-layer structured gradient cemented carbide tool includes a substrate, an intermediate layer and a surface layer, and the intermediate layer is arranged between the substrate and the surface layer;

[0008] Both the substrate and the intermediate layer are made of WC-Co particles, and the surface layer is made of WC-TiC-TaC-Co particles;

[0009] The crystal grains of both the substrate and the surface layer are smaller than those of the intermediate layer.

[0010] A preferred embodiment of the present invention, wherein the thickness of the intermediate layer is 30-100 μm, which is beneficial to improving seismic resistance and impact resistance.

[0011] A preferred embodiment of the present invention, wherein the thickness of the surface layer is 30-200 μm, which is beneficial to reducing the friction coefficient and improving wear resistance.

[0012] A manufacturing method of a laser additive manufacturing double-layer structured gradient cemented carbide tool includes the following steps:

[0013] Obtain spherical cemented carbide particles by the atomization pre-sintering granulation method;

[0014] Optimize the process parameters and environmental parameters of selective laser melting;

[0015] Form the substrate, the intermediate layer and the surface layer in sequence by selective laser melting printing;

[0016] Obtain a double-layer structured gradient cemented carbide tool.

[0017] A preferred embodiment of the present invention, wherein the process route of the atomization pre-sintering granulation method is: powder mixing, ball milling, spraying, pre-sintering, plasma spheroidization.

[0018] Furthermore, in the powder mixing operation, by adjusting the WC crystal grain size, Co content, TiC and TaC content of the cemented carbide powder particles, and the ratio of paraffin, n-heptane and grinding ball content, the composition control of fine-grained WC-Co, coarse-grained WC-Co and fine-grained WC-TiC-TaC-Co cemented carbide powder particles is realized.

[0019] Furthermore, in the pre-sintering operation, the powder is sintered at a maximum temperature of 1200°C to achieve densification inside the hard alloy powder particles, and the morphology of the metal powder material is secondarily modified by high-temperature plasma.

[0020] In addition, Co in the hard alloy material can absorb a large amount of heat during the laser additive manufacturing process, thereby achieving the melting of solid-phase Co (the appearance of liquid-phase Co) and promoting the densification of the hard alloy.

[0021] A preferred embodiment of the present invention, wherein the optimization operation of the process parameters of the selective laser melting is as follows:

[0022] Based on the optimization of the process parameters of the laser additive manufacturing by the response surface method, taking the scanning strategy, laser energy, scanning speed, and scanning spacing of the selective laser melting as the process parameters, a process parameter model for the densification of hard alloy particles is studied.

[0023] A preferred embodiment of the present invention, wherein the optimization operation of the environmental parameters of the selective laser melting is as follows:

[0024] Study the influence of the powder layer thickness on the lap rate of the finished product, and study the influence of the environmental preheating temperature and protective gas control on the microstructure and density.

[0025] The present invention has the following beneficial effects compared with the prior art:

[0026] 1. Development of the powder granulation and spheroidization process for SLM hard alloy: The fine-grained WC-Co, coarse-grained WC-Co, and WC-TiC-TaC-Co hard alloy powder particles are respectively prepared by spray granulation - pre-sintering densification - plasma spheroidization method to improve various powder engineering performance indexes such as the bulk properties, interfacial properties, and surface wettability of the particles.

[0027] 2. Precise control of the microstructure of the hard alloy tool: Based on the selective laser melting additive manufacturing, the near-net shaping of the hard alloy tool is realized, and the gradient microstructure from the surface to the inside of the hard alloy tool (the mutual matching of the wear-resistant surface layer and the tough transition layer) and the size of the V-shaped chip breaker groove are precisely controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a three-dimensional structure schematic diagram of the laser additive manufacturing double-layer structure gradient hard alloy tool of the present invention.

[0029] Figure 2 It is a schematic diagram of the hard alloy powder particles obtained by atomization pre-sintering of the present invention.

[0030] Figure 3 It is a schematic diagram of the hard alloy sample obtained from the hard alloy powder particles of the present invention.

[0031] Figure 4 SEM morphology diagram of the cemented carbide powder particles of the present invention.

[0032] Figure 5 Particle size distribution curve diagram of the cemented carbide powder particles of the present invention.

[0033] Figure 6 Enlarged view of effectively segmenting WC grains by the watershed algorithm of the present invention.

[0034] Figure 7 Simulation diagram of the laser additive manufacturing process of the cemented carbide of the present invention. In the figure, (a) is a randomly generated powder bed model, (b) is a temperature distribution diagram, (c) is a comparison diagram of the simulation and experiment of the molten pool size and surface morphology, and (d) is the molten pool size under different laser parameters. Detailed implementation manners

[0035] In order to enable those skilled in the art to well understand the technical solution of the present invention, the present invention will be further described below in conjunction with embodiments and drawings, but the implementation manners of the present invention are not limited thereto.

[0036] Embodiment 1

[0037] Combined with Figure 1 , the laser additive manufacturing double-layer structure gradient cemented carbide tool of this embodiment includes a substrate 1, an intermediate layer 2 and a surface layer 3. The intermediate layer 2 is arranged between the substrate 1 and the surface layer 3; both the substrate 1 and the intermediate layer 2 are made of WC-Co particles, and the surface layer 3 is made of WC-TiC-TaC-Co particles; the crystal grains of the substrate 1 and the surface layer 3 are both smaller than those of the intermediate layer 2.

[0038] The above three types of conventional cemented carbide powder particles are shown in Table 1 below:

[0039] Table 1 Three types of conventional cemented carbide materials

[0040] Cemented carbide powder particles Ceramic phase (powder FSSS particle size) Metal phase (powder content) Fine-grained WC-Co particles WC (0.6 - 1μm) Co (10 - 20 vol.%) Coarse-grained WC-Co particles WC (3 - 10μm) Co (15 - 25 vol.%) Fine-grained WC-TiC-TaC-Co particles WC / TiC / TaC (0.6 - 1μm) Co (5 - 20 vol.%)

[0041] Furthermore, the layer thickness of the intermediate layer 2 is 30-100 μm, which is beneficial to improving seismic resistance and impact resistance.

[0042] Furthermore, the layer thickness of the surface layer 3 is 30-200 μm, which is beneficial to reducing the friction coefficient and improving the wear resistance.

[0043] The manufacturing method of the laser additive manufacturing double-layer structure gradient cemented carbide tool of this embodiment includes the following steps:

[0044] (1) Spherical cemented carbide particles are obtained by the atomization pre-sintering granulation method; wherein, the process route of the atomization pre-sintering granulation method is: powder mixing, ball milling, spraying, pre-sintering, and plasma spheroidization.

[0045] Furthermore, in the powder mixing operation, by adjusting the WC grain size, Co content, TiC and TaC content of the cemented carbide powder particles, as well as the ratio of paraffin, n-heptane, and grinding ball content, the composition control of fine-grained WC-Co, coarse-grained WC-Co, and fine-grained WC-TiC-TaC-Co cemented carbide powder particles is realized.

[0046] Furthermore, in the pre-sintering operation, the powder is sintered at a maximum temperature of 1200 °C to achieve the densification inside the cemented carbide powder particles, and the morphology of the metal powder material is secondarily modified by high-temperature plasma.

[0047] In addition, Co in the cemented carbide material can absorb a large amount of heat during the laser additive manufacturing process, thereby realizing the melting of solid-phase Co (appearance of liquid-phase Co) and promoting the densification of the cemented carbide.

[0048] (2) Optimize the process parameters of selective laser melting:

[0049] Based on the optimization of the laser additive manufacturing process parameters by the response surface method, with the scanning strategy, laser energy, scanning speed, and scanning spacing of selective laser melting as the process parameters, the process parameter model for the densification of cemented carbide particles is studied.

[0050] Optimize the environmental parameters of selective laser melting:

[0051] Study the influence of the powder layer thickness on the overlap rate of the finished product, and study the influence of the environmental preheating temperature and protective gas control on the microstructure and density.

[0052] (3) Sequentially form a substrate, a transition layer, and a surface layer by selective laser melting printing.

[0053] (4) Obtain a double-layer structure gradient cemented carbide tool.

[0054] Example 2

[0055] After a large number of exploratory experiments on the SLM laser additive manufacturing of cemented carbide, near-spherical cemented carbide powder particles obtained through powder mixing-ball milling-spray granulation experiments and cemented carbide samples obtained through laser additive manufacturing are as Figure 2 - Figure 3 shown. The size distribution of the cemented carbide particles is measured to be good by a malvern laser particle size analyzer (Mastersizer 2000), as Figure 4 - Figure 5As shown in the figure. The research results of SLM laser additive manufacturing of cemented carbide were published in Acta Metallurgica Sinica (English Letters), 2021: 1-10.

[0056] As Figure 6 shown, the watershed algorithm was used to effectively segment WC grains. The main microparameters of cemented carbide were obtained by using computer automatic image processing technology, and were compared and analyzed with the microparameters obtained by the traditional intercept method to explore the relationship between microparameters and hardness, proving the accuracy of this method. At the same time, a microparameter model of WC-Co cemented carbide was established, two-dimensional finite element simulation of the microstructure was carried out, and the Young's modulus and equivalent Poisson's ratio of WC-Co cemented carbide were predicted. The relevant papers were published in Ceramics International, 2017, 43: 14865-14872.

[0057] The process of laser additive manufacturing (SLM) of cemented carbide is complex. Numerical simulation technology is used to simulate the SLM process. The results of numerical simulation can provide a good direction for the formulation of experimental schemes. At the same time, the simulation is also helpful for exploring the microstructure evolution and densification mechanism of cemented carbide. In the early stage of this project, the process of laser additive manufacturing of cemented carbide was simulated, as Figure 7 shown. The simulation results of WC-20Co cemented carbide particles under process parameters such as a laser scanning speed of 350 mm / s and a laser power of 212 W. The research results of relevant SLM laser additive manufacturing of cemented carbide experiments and simulations were published in the doctoral thesis and Powder Metallurgy, 2020, 63(5): 359-366.

[0058] The above are the preferred embodiments of the present invention. However, the embodiments of the present invention are not limited by the above content. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A laser additive manufacturing double-layer structured gradient cemented carbide cutting tool, characterized in that, It includes a substrate, an intermediate layer and a surface layer, and the intermediate layer is disposed between the substrate and the surface layer; Both the substrate and the intermediate layer are made of WC-Co particles, and the surface layer is made of WC-TiC-TaC-Co particles; The grain sizes of both the substrate and the surface layer are smaller than that of the intermediate layer.

2. The laser additive manufacturing double-layer structured gradient cemented carbide tool according to claim 1, wherein, The thickness of the intermediate layer is 30 - 100 μm.

3. The laser additive manufacturing double-layer structured gradient cemented carbide tool according to claim 1, characterized in that, The thickness of the surface layer is 30 - 200 μm.

4. A manufacturing method of the laser additive manufacturing double-layer structured gradient cemented carbide cutting tool according to any one of claims 1-3, characterized in that, It includes the following steps: Spherical cemented carbide particles are obtained by the atomization pre-sintering granulation method; The process parameters and environmental parameters of selective laser melting are optimized; The substrate, the intermediate layer and the surface layer are sequentially formed by selective laser melting printing; A double-layer structure gradient cemented carbide cutting tool is obtained.

5. The manufacturing method according to claim 4, characterized in that, The process route of the atomization pre-sintering granulation method is: powder mixing, ball milling, spraying, pre-sintering, and plasma spheroidization.

6. The manufacturing method according to claim 5, wherein, In the powder mixing operation, the composition control of fine-grained WC-Co, coarse-grained WC-Co and fine-grained WC-TiC-TaC-Co cemented carbide powder particles is realized by adjusting the WC grain size, Co content, TiC and TaC content of the cemented carbide powder particles, as well as the ratio of paraffin, n-heptane and grinding ball content.

7. The manufacturing method according to claim 5, characterized in that, In the pre-sintering operation, the powder is sintered at a maximum temperature of 1200 °C to achieve the densification inside the cemented carbide powder particles, and the morphology of the metal powder material is secondarily modified by high-temperature plasma.

8. The manufacturing method according to claim 4, characterized in that, The optimization operation of the process parameters of the selective laser melting is as follows: Based on the optimization of the process parameters of laser additive manufacturing by the response surface method, with the scanning strategy, laser energy, scanning speed and scanning spacing of selective laser melting as the process parameters, the process parameter model of cemented carbide particle densification is studied.

9. The manufacturing method according to claim 4, wherein The optimization operation of the environmental parameters of the selective laser melting is as follows: The influence of the powder layer thickness on the finished product lap rate is studied, and the influence of the environmental preheating temperature and protective gas control on the microstructure and density is studied.

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