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2025
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Tool coatings CVD and PVD
Since the 1960s, after nearly half a century of development, surface coating technology for cutting tools has become the main method to enhance the performance of cutting tools. The surface coating of cutting tools mainly increases the cutting speed and feed rate by enhancing the surface hardness, thermal stability and reducing the friction coefficient of the cutting tool, thereby improving the cutting efficiency and significantly extending the tool life.
Coating process tool coating technology is generally divided into two major categories: chemical vapor deposition (CVD) and physical vapor deposition (PVD).
1.CVD technology is widely applied in the surface treatment of hard alloy indexable tools. CVD can achieve the deposition of single-component single-layer and multi-component multi-layer composite coatings. The coating has a high bonding strength with the substrate, and the film thickness is relatively thick, reaching 7 to 9 meters, with excellent wear resistance. However, the high temperature of the CVD process can easily lead to a decrease in the bending strength of the tool material; the interior of the coating is in a tensile stress state, which is prone to cause micro-cracks when the tool is in use. Meanwhile, the waste gas and waste liquid discharged by the CVD process can cause significant environmental pollution. To address the issue of high temperature in CVD processes, low-temperature chemical vapor deposition (PCVD) and medium-temperature chemical vapor deposition (MT-CVD) technologies have been successively developed and put into practical use. At present, CVD(including MT-CVD) technology is mainly used for surface coating of carbide indexable inserts. Coated tools are suitable for high-speed rough and semi-finish machining of medium and heavy cutting.
2.PVD technology is mainly applied to the surface treatment of solid carbide tools and high-speed steel tools. Compared with the CVD process, the PVD process has a lower temperature (as low as 80℃), and has basically no effect on the flexural strength of the tool material below 600℃. The internal stress state of the film is compressive stress, which is more suitable for coating precision and complex hard alloy tools. The PVD process has no adverse impact on the environment. PVD coating technology has been widely applied in the coating treatment of hard alloy drill bits, milling cutters, cutting tools, taps, special-shaped cutting tools, welded cutting tools, etc.
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