Carbide products are mostly made of hard alloys with uniform structure. However, with the continuous development of modern industrial technology, the requirements for hard alloy products are constantly improving, and often have different performance requirements in different working parts. For example, rock drill carbide drills are required to be both wear-resistant and impact-resistant. If a drill with high surface hardness and good wear resistance and good toughness and impact resistance can be produced, the performance of the drill is undoubtedly more uniform. The drill is better. In addition, in order to improve the adhesion performance of the cemented carbide substrate and the surface coating, and improve the adhesion and impact resistance of the veneer carbide, the surface of the cemented carbide is required to have good toughness.
The so-called gradient structure or gradient structure alloy refers to an alloy whose composition and structure exhibit regular differences in different parts of the section. Gradient-structured cemented carbides use their special structural or compositional gradients to impart different properties to different parts, giving the overall product excellent overall mechanical properties. The research work of gradient structure cemented carbide began in the late 1970s, and its industrial application was in the late 1980s. The preparation methods of the gradient structure cemented carbide at home and abroad are mostly based on the traditional process, and some special process measures are taken in the process of forming or sintering to obtain special gradient changes, including: binder phase composition or content gradient change. , hard phase grain size or adjacency gradient changes. The most commonly used methods mainly include: composite hard alloy method, powder layer pressing method, metal melt impregnation method, carbon-poor hard alloy carburizing treatment method, and the like.
1 Research and application of foreign gradient structure cemented carbide
Gradient structure cemented carbide products with good toughness and high surface hardness are generally considered to overcome the shortcomings of conventional hard alloys such as wear resistance and toughness. Therefore, in the research and development of improving the surface hardness of cemented carbide products while maintaining or even improving the toughness of the core, a lot of pioneering work has been done abroad. Among them, the most striking is that Sandvik, Sweden, pioneered the development of cobalt-rich DP (Dual Property) alloys in the central region using low-cost carbon-deficient carbide carburizing technology. This technology was first introduced in 1985. He applied for a US patent in the month and was officially authorized in March 1988. The DP alloy technology mainly includes two aspects. Firstly, a WC+λ+η(coxwyc) three-phase abnormal microstructure alloy containing a uniform fine and controllable decarburization phase is prepared, and then the alloy is carburized. The thickness of each gradient layer in the alloy is effectively controlled. Its essence is to change the distribution of the binder phase in the alloy by carburizing treatment on the basis of the uniform distribution of carbon-deficiency η phase cemented carbide, and to give different properties to different parts of the alloy. After the carburization treatment, the phase of the surface layer of the product is eliminated, and the co migrates to the central portion, so that the surface layer co content is low and the core portion still exists and the co content is high. The surface of the cement with a cobalt content gradient distribution has high hardness, good wear resistance, good impact toughness at the core, good wear resistance and toughness of the alloy, and the use effect is significantly improved compared with the conventional products.
Sandvik's mining and engineering tools company developed three DP spheroidal alloy brands in the late 1980s, DP55, DP60 and DP65. Its wear resistance and toughness are significantly improved compared with traditional alloys, and the working life is three times higher than that of traditional cemented carbide. For example, in the limestone tunnel borehole, a 45 mm impact drill with DP55 conical ball teeth is used, with a drilling speed of 1.96 m·min and an average life of 3121 m; whereas the original cemented carbide ball bit The drilling speed and average life are 1.48m·min and 1000 m respectively. The DP60 heavy-duty ball-toothed drill has an average life of 83m when punched in quartz ore, while the original carbide tipped bit has a life of only 53m. With its excellent performance, DP products have been put into the market for six years in 1986, accounting for 30% to 40% of the total output of cemented carbide cylinders.
Since Sandvik's DP alloy is a patented technology, there is no detailed report on the basic research work directly related to DP alloy in foreign countries. The strengthening mechanism is simply explained by the qualitative analysis of the internal stress distribution state of the alloy. Nevertheless, the carbon-deficient hard alloy carburizing technology used in the alloy solves the contradiction that the wear resistance and toughness of the cemented carbide product are difficult to be considered at the same time, so that the service life of the alloy is significantly improved, and the process is flexible and simple. Features, suitable for industrial production; using a simple sintering and heat treatment method, a gradient structure alloy with a controllable change of the binder phase and a gradient distribution is obtained in a single grade homogeneous cemented carbide, which is obviously obtained in different parts of the cemented carbide sintered body. Different wear resistance and toughness.
Recently, most foreign studies have used the sintering and heat treatment processes to grade the cemented carbide products. The treatment method for controlling the nitrogen content of Ti(CN)-based cermets is a hot research field in current research.
Zackrisson et al. conducted research on nitriding treatment on the surface of cemented carbide to further improve the wear resistance of the surface of cemented carbide. They use the composition series Ti(C,N). TiN. WC. Co+ carbon black, which was first sintered at 1430 ° C for 90 min, and then kept at 1200 0 c for 20 h in a 0.1 MPa nitrogen furnace. The composition of the sample was analyzed by electron probe (EPMA). The surface of the material after nitriding treatment was rich in Ti and N, poor in w and C; from about 40 mm from the surface to the heart, the w content was It is higher than the material not treated by nitriding; its co content is higher than the average co content of the material in the range of 15 to 40 ptm from the surface. At the same time, the surface of the material forms a fine WC phase and a T) phase with a grain size of about 150 nm. The cutting test of SS2541 steel, after the nitriding of the cemented carbide insert, the rate of change of the flank wear (VB) with time is much lower than that of the PVD coated cemented carbide insert (class code P15). It can be seen that the wear resistance and durability of the cemented carbide blade after nitriding treatment are significantly improved compared with the PVD coated blade.
Japan's Senkou Xiushu, etc., firstly mix the TiCN, WC, Co, Ni powder for 24 h, and press the ball mill powder into a 10 mm × 10 mm × 5 mm test piece under a pressure of 98 MPa, and vacuum-sinter at 1400 °C. After holding for 1 h in nitrogen, it was cooled at a suitable speed to prepare a gradient structure cemented carbide having a gradient distribution of co content. The treated material has a co-content increase from the top to the bottom, and a tens of micron TiCN layer is formed on the surface layer. The outer layer of the material contains almost no co, and the highest hardness can reach 2.2GPa. At the same time, the suitable cooling rate makes the surface introduce residual stress of 0.5GPa or more, which greatly improves the resistance to hot cracking of the alloy tool during cutting. performance. The cutting test of the gears and piston rods of the Japanese steel grades SCr420H, s45C, cCM420, SCr420 were carried out. The results show that the cutting life of the developed cemented carbide tool is 2-4 times that of the ordinary TiCN cermet tool.
Suzuki et al. of the University of Tokyo prepared a WC-Ti(C,N)-Co cemented carbide material by a gradient sintering method under a nitrogen removal atmosphere. After sintering, the Ti(C,N) on the surface of the cemented carbide disappears, and part of the binder phase is transferred from the core to the surface to form a binder-rich phase layer. Through the denitrification treatment of the surface of the cemented carbide, a binder phase enrichment is formed on the surface, and the gradient transition layer of the cubic structure carbonitride is eliminated, and the toughness and ductility of the surface of the cemented carbide can be improved.
Based on the results of Suzuki et al., Schwarzkopf et al. of the Max Planck Society of Germany pointed out that the formation of the gradient region of the cemented carbide surface is the result of the thermodynamic coupling of the diffusion of N atoms to the outside of the block and the diffusion of 1 ri atoms into the core of the block. At the same time, Schwarzkopf et al. established a computer model to predict and describe the effects of several important variables in the sintering process. They pointed out that the depth formed by the surface gradient region is proportional to the diffusion law and the root of the sintering time t and the co-content of the matrix. x = kt (1) where is the gradient layer thickness, t is the sintering time, and k is a constant, the value of which is proportional to the co content in the matrix.
In recent years, Chalmers University of Technology in Sweden and Frykholm of the University of Gothenburg have conducted more in-depth research on this surface denitrification gradient modification, and more effectively control the formation of surface denitrification gradient layer. They used scanning electron microscopy (SEM) and electron probe (EMPA) to analyze the microscopic morphology and composition of the surface gradient region and computer simulation. The results show that the experimental analysis results are in good agreement with the computer simulation results.
In addition, DrakeEric of REED ROCK BIT, Colin of the Catholic University of Leuven, Favrot of the French School of Mines, Rosso and Proto of the Polytechnic University of Turin, and Nicolae of the Institute of Metallurgical Studies of Bucharest, respectively, use different hybrid methods. The cemented carbide powders with different grain sizes and Co contents are layered and distributed by solid phase or liquid phase sintering to form a powder with a high Co content from the core and a large grain size of the hard phase, and a low Co content to the surface layer. A powder-transformed gradient structure cemented carbide product having a small hard grain size. The surface of the sample after sintering is fine in grain, low in Co content, high in hardness and good in wear resistance, and gradually transitions to coarse core grains, high co content, good toughness and good impact resistance. The bonding between the powder layers is good, and the residual compressive stress generated after sintering effectively increases the fatigue strength of the product. Gasik of Helsinki University of Technology has used the infiltration method to prepare WC-Co gradient structure cemented carbide. The sample is dense and has a good gradient structure and hardness distribution.
2 Research and application of domestic gradient cemented carbides The successful application of DP alloys has prompted many domestic scholars to explore and study the carbon-poor hard alloy carburizing technology. In recent years, Zhou Jianhua and Sun Baoqi of the Powder Metallurgical Plant of Central South University, Yang Weicai, State Key Laboratory of Powder Metallurgy, and Qi Weijian, Zhuzhou Cemented Carbide Plant, have successfully prepared gradient structure cemented carbide by carbon-poor hard alloy carburizing technology. Good gradient of cobalt phase composition. Sun Xuxin et al. used a carbon-rich potential sintering process to prepare a graded-structured cemented carbide on the basis of carbon-free hard alloy carburizing technology. Firstly, a WC-co alloy mixture which is much lower than the normal carbon content is prepared, and then the carbon-rich potential is sintered to form a carbon gradient with a high surface carbon potential and a low internal carbon potential from the surface to the inside. Thus, when entering the liquid phase sintering stage, the liquid phase first appears on the surface, the liquid phase appears inside, and the liquid phase on the surface is also larger than the internal liquid phase, forming a liquid phase pressure difference between the surface and the interior of the alloy. The mass shift of the Co phase from the surface to the inside forms a reasonable composition gradient. The experimental results show that the above-mentioned carbon-rich potential sintering process can produce a gradient structure cemented carbide with high surface hardness, good wear resistance, high internal strength and good toughness.
Qi Tongchun et al. used DC plasma jet CVD method to deposit diamond film on the surface of cemented carbide. It was found that the chemically etched cemented carbide surface WC particles were decarburized by plasma etching to form equiaxed fine pure w crystal. The granules then form a fine WC layer in the outer surface of the cemented carbide during the deposition of the diamond film, and the WC particle size and the binder phase co content are in an increasing gradient from the surface to the inside. At present, the new plasma surface modification technology is being used to carry out systematic research work on in-situ gradient and nanometer modification of cemented carbide surfaces, and breakthroughs have been made. After the new plasma modified composite treatment, the surface of the YG system (WC 3% to 25% Co) cemented carbide is in-situ WC nano-refinement, the average size of the sub-crystal is 20-30 nm, and the average grain size is 80 100 nm. WC-20%~25% Fe/Co/Ni steel cemented carbide surface WC subgrain average size 20~30 nm, average grain size 100~120 nm.
Cheng Jigui and Xia Yonghong of Hefei University of Technology and Sun Mingjun of Dalian Cemented Carbide Factory have prepared gradient cemented carbide by powder layered hot pressing or sintering method. The results show that the graded structure cemented carbide has good comprehensive mechanical properties.
3 Prospect Gradient Structure Cemented carbides use compositional or structural gradients to achieve performance gradient changes, giving the cemented carbide products excellent overall performance and performance. It is an effective way to solve the contradiction between hard wear resistance and toughness of cemented carbide products. one. Numerous studies have shown that graded-structured cemented carbides are used as direct engineering applications or as superhard coatings (eg CVD diamond coatings, diamond-like carbon coatings, etc.) compared to conventional homogeneous cemented carbides. The base materials of TiN-based coatings, etc. all have the technical characteristics of the display column and broad application prospects.
It should be noted that in the preparation method of the gradient structure cemented carbide, the composite cemented carbide method and the powder layered pressing method are prone to incomplete densification or homogenization during the sintering process; the metal melt impregnation method requires special The device prepares a metal foil body and performs immersion treatment, and the process is complicated. In recent years, the use of sintering and heat treatment technology, the gradient treatment of cemented carbide products, especially the gradient treatment technology of cemented carbide surface (such as nitriding treatment technology, plasma modification technology, etc.), is increasingly receiving domestic The attention of outside researchers. The advantage of the cemented carbide surface gradient treatment technology is that the process is relatively simple, and while maintaining the inherent properties of the cemented carbide block, the surface layer has high performance and versatility, and the service life of the cemented carbide product is remarkably improved.
It can be foreseen that the gradient structure cemented carbide will be one of the key development directions in the field of cemented carbide with its excellent comprehensive performance and low production cost; the development of cemented carbide surface gradient and nanotechnology is cemented carbide. One of the new research directions in the field.
The so-called gradient structure or gradient structure alloy refers to an alloy whose composition and structure exhibit regular differences in different parts of the section. Gradient-structured cemented carbides use their special structural or compositional gradients to impart different properties to different parts, giving the overall product excellent overall mechanical properties. The research work of gradient structure cemented carbide began in the late 1970s, and its industrial application was in the late 1980s. The preparation methods of the gradient structure cemented carbide at home and abroad are mostly based on the traditional process, and some special process measures are taken in the process of forming or sintering to obtain special gradient changes, including: binder phase composition or content gradient change. , hard phase grain size or adjacency gradient changes. The most commonly used methods mainly include: composite hard alloy method, powder layer pressing method, metal melt impregnation method, carbon-poor hard alloy carburizing treatment method, and the like.
1 Research and application of foreign gradient structure cemented carbide
Gradient structure cemented carbide products with good toughness and high surface hardness are generally considered to overcome the shortcomings of conventional hard alloys such as wear resistance and toughness. Therefore, in the research and development of improving the surface hardness of cemented carbide products while maintaining or even improving the toughness of the core, a lot of pioneering work has been done abroad. Among them, the most striking is that Sandvik, Sweden, pioneered the development of cobalt-rich DP (Dual Property) alloys in the central region using low-cost carbon-deficient carbide carburizing technology. This technology was first introduced in 1985. He applied for a US patent in the month and was officially authorized in March 1988. The DP alloy technology mainly includes two aspects. Firstly, a WC+λ+η(coxwyc) three-phase abnormal microstructure alloy containing a uniform fine and controllable decarburization phase is prepared, and then the alloy is carburized. The thickness of each gradient layer in the alloy is effectively controlled. Its essence is to change the distribution of the binder phase in the alloy by carburizing treatment on the basis of the uniform distribution of carbon-deficiency η phase cemented carbide, and to give different properties to different parts of the alloy. After the carburization treatment, the phase of the surface layer of the product is eliminated, and the co migrates to the central portion, so that the surface layer co content is low and the core portion still exists and the co content is high. The surface of the cement with a cobalt content gradient distribution has high hardness, good wear resistance, good impact toughness at the core, good wear resistance and toughness of the alloy, and the use effect is significantly improved compared with the conventional products.
Sandvik's mining and engineering tools company developed three DP spheroidal alloy brands in the late 1980s, DP55, DP60 and DP65. Its wear resistance and toughness are significantly improved compared with traditional alloys, and the working life is three times higher than that of traditional cemented carbide. For example, in the limestone tunnel borehole, a 45 mm impact drill with DP55 conical ball teeth is used, with a drilling speed of 1.96 m·min and an average life of 3121 m; whereas the original cemented carbide ball bit The drilling speed and average life are 1.48m·min and 1000 m respectively. The DP60 heavy-duty ball-toothed drill has an average life of 83m when punched in quartz ore, while the original carbide tipped bit has a life of only 53m. With its excellent performance, DP products have been put into the market for six years in 1986, accounting for 30% to 40% of the total output of cemented carbide cylinders.
Since Sandvik's DP alloy is a patented technology, there is no detailed report on the basic research work directly related to DP alloy in foreign countries. The strengthening mechanism is simply explained by the qualitative analysis of the internal stress distribution state of the alloy. Nevertheless, the carbon-deficient hard alloy carburizing technology used in the alloy solves the contradiction that the wear resistance and toughness of the cemented carbide product are difficult to be considered at the same time, so that the service life of the alloy is significantly improved, and the process is flexible and simple. Features, suitable for industrial production; using a simple sintering and heat treatment method, a gradient structure alloy with a controllable change of the binder phase and a gradient distribution is obtained in a single grade homogeneous cemented carbide, which is obviously obtained in different parts of the cemented carbide sintered body. Different wear resistance and toughness.
Recently, most foreign studies have used the sintering and heat treatment processes to grade the cemented carbide products. The treatment method for controlling the nitrogen content of Ti(CN)-based cermets is a hot research field in current research.
Zackrisson et al. conducted research on nitriding treatment on the surface of cemented carbide to further improve the wear resistance of the surface of cemented carbide. They use the composition series Ti(C,N). TiN. WC. Co+ carbon black, which was first sintered at 1430 ° C for 90 min, and then kept at 1200 0 c for 20 h in a 0.1 MPa nitrogen furnace. The composition of the sample was analyzed by electron probe (EPMA). The surface of the material after nitriding treatment was rich in Ti and N, poor in w and C; from about 40 mm from the surface to the heart, the w content was It is higher than the material not treated by nitriding; its co content is higher than the average co content of the material in the range of 15 to 40 ptm from the surface. At the same time, the surface of the material forms a fine WC phase and a T) phase with a grain size of about 150 nm. The cutting test of SS2541 steel, after the nitriding of the cemented carbide insert, the rate of change of the flank wear (VB) with time is much lower than that of the PVD coated cemented carbide insert (class code P15). It can be seen that the wear resistance and durability of the cemented carbide blade after nitriding treatment are significantly improved compared with the PVD coated blade.
Japan's Senkou Xiushu, etc., firstly mix the TiCN, WC, Co, Ni powder for 24 h, and press the ball mill powder into a 10 mm × 10 mm × 5 mm test piece under a pressure of 98 MPa, and vacuum-sinter at 1400 °C. After holding for 1 h in nitrogen, it was cooled at a suitable speed to prepare a gradient structure cemented carbide having a gradient distribution of co content. The treated material has a co-content increase from the top to the bottom, and a tens of micron TiCN layer is formed on the surface layer. The outer layer of the material contains almost no co, and the highest hardness can reach 2.2GPa. At the same time, the suitable cooling rate makes the surface introduce residual stress of 0.5GPa or more, which greatly improves the resistance to hot cracking of the alloy tool during cutting. performance. The cutting test of the gears and piston rods of the Japanese steel grades SCr420H, s45C, cCM420, SCr420 were carried out. The results show that the cutting life of the developed cemented carbide tool is 2-4 times that of the ordinary TiCN cermet tool.
Suzuki et al. of the University of Tokyo prepared a WC-Ti(C,N)-Co cemented carbide material by a gradient sintering method under a nitrogen removal atmosphere. After sintering, the Ti(C,N) on the surface of the cemented carbide disappears, and part of the binder phase is transferred from the core to the surface to form a binder-rich phase layer. Through the denitrification treatment of the surface of the cemented carbide, a binder phase enrichment is formed on the surface, and the gradient transition layer of the cubic structure carbonitride is eliminated, and the toughness and ductility of the surface of the cemented carbide can be improved.
Based on the results of Suzuki et al., Schwarzkopf et al. of the Max Planck Society of Germany pointed out that the formation of the gradient region of the cemented carbide surface is the result of the thermodynamic coupling of the diffusion of N atoms to the outside of the block and the diffusion of 1 ri atoms into the core of the block. At the same time, Schwarzkopf et al. established a computer model to predict and describe the effects of several important variables in the sintering process. They pointed out that the depth formed by the surface gradient region is proportional to the diffusion law and the root of the sintering time t and the co-content of the matrix. x = kt (1) where is the gradient layer thickness, t is the sintering time, and k is a constant, the value of which is proportional to the co content in the matrix.
In recent years, Chalmers University of Technology in Sweden and Frykholm of the University of Gothenburg have conducted more in-depth research on this surface denitrification gradient modification, and more effectively control the formation of surface denitrification gradient layer. They used scanning electron microscopy (SEM) and electron probe (EMPA) to analyze the microscopic morphology and composition of the surface gradient region and computer simulation. The results show that the experimental analysis results are in good agreement with the computer simulation results.
In addition, DrakeEric of REED ROCK BIT, Colin of the Catholic University of Leuven, Favrot of the French School of Mines, Rosso and Proto of the Polytechnic University of Turin, and Nicolae of the Institute of Metallurgical Studies of Bucharest, respectively, use different hybrid methods. The cemented carbide powders with different grain sizes and Co contents are layered and distributed by solid phase or liquid phase sintering to form a powder with a high Co content from the core and a large grain size of the hard phase, and a low Co content to the surface layer. A powder-transformed gradient structure cemented carbide product having a small hard grain size. The surface of the sample after sintering is fine in grain, low in Co content, high in hardness and good in wear resistance, and gradually transitions to coarse core grains, high co content, good toughness and good impact resistance. The bonding between the powder layers is good, and the residual compressive stress generated after sintering effectively increases the fatigue strength of the product. Gasik of Helsinki University of Technology has used the infiltration method to prepare WC-Co gradient structure cemented carbide. The sample is dense and has a good gradient structure and hardness distribution.
2 Research and application of domestic gradient cemented carbides The successful application of DP alloys has prompted many domestic scholars to explore and study the carbon-poor hard alloy carburizing technology. In recent years, Zhou Jianhua and Sun Baoqi of the Powder Metallurgical Plant of Central South University, Yang Weicai, State Key Laboratory of Powder Metallurgy, and Qi Weijian, Zhuzhou Cemented Carbide Plant, have successfully prepared gradient structure cemented carbide by carbon-poor hard alloy carburizing technology. Good gradient of cobalt phase composition. Sun Xuxin et al. used a carbon-rich potential sintering process to prepare a graded-structured cemented carbide on the basis of carbon-free hard alloy carburizing technology. Firstly, a WC-co alloy mixture which is much lower than the normal carbon content is prepared, and then the carbon-rich potential is sintered to form a carbon gradient with a high surface carbon potential and a low internal carbon potential from the surface to the inside. Thus, when entering the liquid phase sintering stage, the liquid phase first appears on the surface, the liquid phase appears inside, and the liquid phase on the surface is also larger than the internal liquid phase, forming a liquid phase pressure difference between the surface and the interior of the alloy. The mass shift of the Co phase from the surface to the inside forms a reasonable composition gradient. The experimental results show that the above-mentioned carbon-rich potential sintering process can produce a gradient structure cemented carbide with high surface hardness, good wear resistance, high internal strength and good toughness.
Qi Tongchun et al. used DC plasma jet CVD method to deposit diamond film on the surface of cemented carbide. It was found that the chemically etched cemented carbide surface WC particles were decarburized by plasma etching to form equiaxed fine pure w crystal. The granules then form a fine WC layer in the outer surface of the cemented carbide during the deposition of the diamond film, and the WC particle size and the binder phase co content are in an increasing gradient from the surface to the inside. At present, the new plasma surface modification technology is being used to carry out systematic research work on in-situ gradient and nanometer modification of cemented carbide surfaces, and breakthroughs have been made. After the new plasma modified composite treatment, the surface of the YG system (WC 3% to 25% Co) cemented carbide is in-situ WC nano-refinement, the average size of the sub-crystal is 20-30 nm, and the average grain size is 80 100 nm. WC-20%~25% Fe/Co/Ni steel cemented carbide surface WC subgrain average size 20~30 nm, average grain size 100~120 nm.
Cheng Jigui and Xia Yonghong of Hefei University of Technology and Sun Mingjun of Dalian Cemented Carbide Factory have prepared gradient cemented carbide by powder layered hot pressing or sintering method. The results show that the graded structure cemented carbide has good comprehensive mechanical properties.
3 Prospect Gradient Structure Cemented carbides use compositional or structural gradients to achieve performance gradient changes, giving the cemented carbide products excellent overall performance and performance. It is an effective way to solve the contradiction between hard wear resistance and toughness of cemented carbide products. one. Numerous studies have shown that graded-structured cemented carbides are used as direct engineering applications or as superhard coatings (eg CVD diamond coatings, diamond-like carbon coatings, etc.) compared to conventional homogeneous cemented carbides. The base materials of TiN-based coatings, etc. all have the technical characteristics of the display column and broad application prospects.
It should be noted that in the preparation method of the gradient structure cemented carbide, the composite cemented carbide method and the powder layered pressing method are prone to incomplete densification or homogenization during the sintering process; the metal melt impregnation method requires special The device prepares a metal foil body and performs immersion treatment, and the process is complicated. In recent years, the use of sintering and heat treatment technology, the gradient treatment of cemented carbide products, especially the gradient treatment technology of cemented carbide surface (such as nitriding treatment technology, plasma modification technology, etc.), is increasingly receiving domestic The attention of outside researchers. The advantage of the cemented carbide surface gradient treatment technology is that the process is relatively simple, and while maintaining the inherent properties of the cemented carbide block, the surface layer has high performance and versatility, and the service life of the cemented carbide product is remarkably improved.
It can be foreseen that the gradient structure cemented carbide will be one of the key development directions in the field of cemented carbide with its excellent comprehensive performance and low production cost; the development of cemented carbide surface gradient and nanotechnology is cemented carbide. One of the new research directions in the field.
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