Role of argon in its mixture with nitrogen in deposition of nitride condensates in the Ti-Si-N system and in vacuum arc deposition processes

Abstract

Arc vacuum deposition of nitride coatings in the Ti-Si-N system is carried out in an argonnitrogen mixture with variable gas concentration ratios. The resulting condensates are studied by fractographic analysis, X-ray diffraction analysis, and high-resolution scanning electron microscopy. Studied also are the elemental composition and microhardness of the condensates. At gas mixture pressure p > 5 × 10−3 Torr, conditions are found under which the hardness of the condensates is maximal, and the dependence of the hardness on the argon percentage in the mixture is obtained. At an argon percentage of 8–12%, the hardness of the coatings reaches 50 GPa. This value is 1.7 times higher than the hardness of coatings obtained in a nitrogen atmosphere. This superhard state is explained by the nanometer size (25–30 nm) of nitride grains and a specific growing texture with a family of {100} planes that is parallel to the growth plane. Such a configuration minimizes the surface energy. Mechanisms that may increase the ionization of film-forming particles and activate chemical bonds in the presence of argon are discussed.