Influence of Substrate Hardness on the Properties of PVD Hard Coatings

Nowadays, hard coatings based on transition metal nitrides are extensively used for materials protection and particularly to improve the lifetime and performance of various cutting and forming tools. Practically, hard coatings need to be deposited on different kinds of substrate materials in different application areas. The physical properties, such as hardness, of the substrate may have evident influence on the properties and performance of the hard coatings. In this work, different kinds of hard coatings, including TiN, CrN, TiAlN, and CrAlN, were deposited by a lateral rotating cathode arc technique on two kinds of steel substrates with different hardness. The composition, crystalline structure, mechanical and tribological properties of the as‐deposited hard coatings were systematically analyzed by energy dispersive analysis of X‐rays, X‐ray diffraction, nanoindentation, pin‐on‐disc tribometer, Rockwell indentation, and scratch test, respectively. The influence of substrate hardness on the properties of the hard coatings was investigated. It was found that the substrate hardness has little influence on the crystalline structure, nano‐hardness, and tribological properties (friction coefficient and wear rate). However, it showed a significant effect of the toughness and adhesion of the hard coatings. It can be concluded that hard coatings need to be supported by hard substrates.

Keywords:

• mechanical properties
• tribological properties
• nitride hard coatings
• lateral rotating cathode arc deposition

Acknowledgments

The authors would like to thank Mr. Anthony Yeo for his technical assistance in this work.