Physical vapor deposition coating occurred in the late 1970s. Its successful application in the field of high-speed steel cutting tools attracted the attention of the world. While people competing to develop high-performance, high-reliability coating equipment, the further expansion of the application field has been lead to more in-depth research, especially for carbide and ceramic cutting tools.
PVD (Physical Vapor Deposition) coatings have the following advantages:
◆ Compared with the chemical vapor deposition coating, the physical vapor deposition coating has a lower temperature, generally below 600°C, and it has little effect on the bending strength of the tool material.
◆ The inside of the coating is in the state of compressive stress, so it is more suitable for hard alloy precision complex tools.
◆ No pollution to the environment, in line with the current development direction of the green industry.
◆ The emergence of nano-scale coatings has made new breakthroughs in physical vapor deposition coating for tool quality. This nano-scale coating has tha advantages of high binding strength, high hardness and good oxidation resistance, also it can effectively control the edge shape and accuracy of the precision tool.
Although the physical vapor deposition coating has the above advantages, there are some drawbacks:
◆ The coating equipment is complex and expensive, it has high requirements for process, long coating time, and increased tool cost.
◆ The geometry of coating tool is single, so its superiority is limiting.
◆ Internal stress and micro-cracks are generated due to the different shrinkage rates of the coating and the substrate during cooling.
◆ Very small inner holes and narrow gaps cannot be coated.