Abstract In recent years, the rapid advancement of science and technology has driven the development of advanced materials for industrial applications. Among these, cemented carbide is widely used in cutting tools, plain bearings, tensile dies, and other wear-resistant components due to its excellent hardness and durability. However, as machining processes become more demanding, traditional cemented carbide tools often face challenges in balancing wear resistance with toughness. To meet the growing demands for high-efficiency, high-precision, and reliable machining, it is essential to enhance the overall performance of tool materials.
The manufacturing industry is also pushing for innovation in tool design, aiming to develop new high-performance, long-lasting products that can boost market growth. Research has identified several key areas for improving cemented carbide tools:
(1) Refining the grain size of the material to increase the surface area and bonding strength between hard phases, thereby enhancing mechanical properties. However, the refining process is still immature and costly, which limits widespread application.
(2) Surface heat treatment to modify the binder phase composition and structure, aiming to improve both strength and toughness. While this method can help reduce internal stress, its overall effectiveness remains limited.
(3) Strengthening the hard phase by adding rare or rare-earth metals, which can further improve chip performance and tool life.
(4) Coating cemented carbide tools with thin layers of wear-resistant materials such as TiC, TiAlN, Al₂O₃, or diamond using techniques like CVD, PVD, or HVOF. These coatings combine the high hardness and wear resistance of the coating with the toughness of the substrate, significantly extending tool life and revolutionizing cutting technology.
Diamond, being the hardest natural material, possesses unique properties such as low friction, high thermal conductivity, and chemical stability, making it ideal for abrasive and cutting applications. However, single-crystal diamond tools are brittle and expensive, limiting their use. Meanwhile, diamond films offer a more cost-effective alternative. When combined with cemented carbide substrates, they provide a balance of high hardness, wear resistance, and impact toughness at a lower cost, making them highly valuable in modern machining.
Studies show that diamond coatings can greatly enhance the performance of cemented carbide tools, especially when machining non-ferrous metals, composites, and ceramics, increasing tool life by dozens of times. The CVD method allows for precise control over film quality, making it suitable for complex geometries. Leading companies like sp³, Cemecon, Balzers, and OSG have developed advanced CVD diamond-coated tools, which are now widely used in precision industries such as automotive, aerospace, and electronics. Despite this, China still lags behind in this field, highlighting the need for further research and development.
Research on CVD diamond coating technology began in the 1950s, with significant progress made over the decades. Initially, natural diamonds were used, but later, synthetic methods like PCD (Polycrystalline Diamond) and CVD allowed for larger, more durable tools. Today, CVD diamond coatings are mature and widely applied, with ongoing efforts to improve adhesion, deposition quality, and cost-effectiveness.
The preparation of CVD diamond coatings involves various methods, including hot filament CVD, microwave plasma CVD, and DC arc plasma jet. Hot filament CVD is the most common due to its cost-effectiveness and controllability, while microwave methods offer higher quality but at a higher price. DC plasma jet provides fast deposition rates, making it suitable for large-scale production.
The presence of cobalt in cemented carbide substrates poses challenges for diamond deposition, as it can promote graphitization and reduce adhesion. Researchers have explored ways to mitigate this, such as surface pretreatment, gradient carbide structures, and the addition of transition layers. These methods aim to improve adhesion and ensure stable diamond growth.
In conclusion, the development of CVD diamond-coated tools represents a significant advancement in machining technology. With continued improvements in coating quality, adhesion, and cost, these tools are set to play an even greater role in the future of industrial manufacturing.
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