Since the 1960s, CVD technology has been widely used for the surface treatment of carbide indexable tools. In the mid-to-late 1980s, 85% of cemented carbide tools in the United States were treated with a surface coating, of which CVD coatings accounted for 99%. By the mid-1990s, CVD coated carbide inserts were used in coated carbide tools. Still accounted for more than 80%. Previous Next
In the late 1980s, the low temperature chemical vapor deposition (PCVD) technology developed by Krupp.Widia reached a practical level. The processing temperature has been reduced to 450~650 °C, which effectively controls the generation of η phase. It can be used for screwdrivers, milling cutters, The molds are coated with TiN, TiCN, TiC, etc., but so far, the application of PCVD in the field of tool coating is not extensive.
In the mid-1990s, the emergence of new technologies for medium temperature chemical vapor deposition (MTCVD) revolutionized CVD technology. A coating of a dense fibrous crystalline form can be obtained by MTCVD. The coating thickness can reach 8~10μm. This coating structure has extremely high wear resistance, thermal shock resistance and toughness. MTCVD coated carbide inserts are suitable for use in high temperature, high speed, high load, dry cutting conditions, and their service life can be doubled compared to conventional coated carbide inserts.
China began to study CVD coating technology in the early 1970s. Due to the strong specificity of this technology, there are not many units engaged in research in China. In the mid-1980s, the development of China's CVD tool coating technology reached a practical level, and the level of process technology was comparable to the international level at that time, but it developed slowly in the following decade. The research of low temperature chemical vapor deposition (PCVD) technology in China began in the early 1990s. PCVD technology is mainly used for mold coating, and its application in the field of cutting tools is also very limited. In the late 1990s, China began research and development of medium temperature chemical vapor deposition (MTCVD) technology.
3. Physical vapor deposition (PVD) technology
Physical vapor deposition is mainly composed of three types of evaporation coating, ion plating and sputtering coating. Vacuum evaporation coating is a kind of PVD coating technology that has developed earlier and is the most widely used. It still occupies 40% of the world market, but its application range is shrinking. This technique uses a heating coating material such as a resistor or an electron beam under vacuum conditions to melt and evaporate it and deposit it on the surface of the alloy substrate to form a coating film.
In the ion plating film, Ar gas or the like is introduced under vacuum, and the gas and the plating material portion are separated by glow discharge, and the ion bombardment target strikes the material ions on the target to deposit on the surface of the alloy substrate. The most successful application of ion plating in the coating of superhard materials for cutting tools is multi-arc ion plating.
The sputter coating is a technique in which a surface of a target is bombarded with a charge ion in a vacuum chamber, and atoms and other particles in the target are bombarded by ion momentum transfer, and deposited on the surface of the alloy substrate to form a coating. Sputter coating enables rapid deposition over large areas.
PVD technology appeared in the late 1970s and can be used as a final treatment process for the coating of high speed steel tools because its process temperature can be controlled below 500 °C. Since PVD technology can greatly improve the cutting performance of high-speed steel tools, this technology has been rapidly promoted since the 1980s.