Study of thermal stability of some hard nitride coatings deposited by reactive magnetron sputtering

The thermal stability of Cr2Nx, CrNx, TiN and TiNx(B)(y) coatings was inves tigated in the temperature range of 300-1300 K, by characterization of thei r microstructural changes and oxidation behaviour. The microstructural chan ges were studied by high temperature X-ray diffraction under vacuum conditi ons (10(-3) Pa). The increase of temperature induces grain growth, crystall ization of amorphous phase, phase decomposition and oxidation. All these ph enomena appear at different temperatures depending on the coating material. The effects of annealing temperature on mechanical properties were charact erized by means of the scratch test and Vicker's microhardness. Different e volutions of the critical load and microhardness were observed for each coa ting. Some relations between evolutions of the mechanical properties and th e microstructure have been identified. The oxidation temperature of Ti-base d coatings deposited on alumina substrates was determined by thermal gravim etric analysis. The highest thermal stability was observed for TiNx(B)(y) c oatings, according to microstructure, oxidation resistance and mechanical p roperties. (C) 1999 Elsevier Science S.A. All rights reserved.