Physical-mechanical properties of superhard nanocomposite coatings on base Zr-Ti-Si-N

Abstract

Hard and super hard coatings of Zr-Ti-Si-N of from 2.8 μm to 3.5 μm thickness were fabricated using a vacuum arc source with high frequency stimulation. The samples were annealed in vacuum and in air at 1200 °C. It was found that films with a high Zr and Ti content were thermally stable up to 1180 °C. At the same time, a thin oxide layer of 180 nm to 240 nm was found on the surfaces, which protected the sample from destruction. Below 1000 °C annealing temperature in vacuum, changing of phase composition is determined by appearing of siliconitride crystallites (ß-Si3N4) with hexagonal crystalline lattice and by formation of ZrO2 oxide crystallites. Size of grains of a substitution solid solution (Zr, Ti)N varied from (10 - 12) nm to 25 nm, but Ti concentration in the solid solution increased. In the process of annealing, hardness of the best series of samples increased from (39.6 ±1.4) GPa to 53.6 GPa, which seemed to indicate that a spinodal segregation along grain interfaces was finished.