Multilayer Hard Coating via CVD for Wear Resistance

The patent replaces the PVD (Physical Vapor Deposition) mechanical/physical process with a CVD (Chemical Vapor Deposition) chemical process. In CVD, titanium and aluminum chlorides react chemically with ammonia or nitrogen-containing gases to form TiN and AlN coatings through chemical reactions, eliminating the mechanical ejection and condensation process that generates droplets and impurities in PVD methods.

The patent changes the fundamental deposition mechanism from physical vapor deposition to chemical vapor deposition. This parameter change transforms the coating formation process from a physical ejection-condensation process to a chemical reaction-deposition process, thereby eliminating the generation of metallic droplets and impurities that occur in PVD methods.

The patent divides the single-layer TiAlN coating into multiple alternating layers of TiN and AlN. This segmentation creates a multilayer structure where each layer contributes different properties: TiN layers provide hardness and wear resistance, while AlN layers provide thermal stability and oxidation resistance. The layered structure also improves adhesion through intermediate composition layers.

The patent creates a composite coating structure by alternating TiN and AlN layers. This composite material approach combines the advantages of both materials: TiN contributes high hardness and wear resistance, while AlN contributes thermal stability and oxidation resistance, resulting in a coating with superior overall performance under high-speed working conditions.

The patent applies different material compositions to different layers of the coating to address specific local requirements. The TiN layers provide local hardness and wear resistance at the cutting edge surface, while the AlN layers provide local thermal stability and oxidation resistance deeper in the coating structure, allowing the coating to withstand high-temperature and high-pressure environments during high-speed working.

The alternating TiN and AlN layered structure creates a composite material system that simultaneously provides wear resistance from TiN and thermal stability from AlN, enabling the coating to maintain its protective function under the combined high-temperature and high-pressure conditions encountered during high-speed metal working, thereby extending service life while maintaining high productivity.