Microstructure, oxidation resistance, mechanical and tribological properties of Ti–Y–N films by reactive magnetron sputtering

Abstract

Composite Ti–Y–N films with various Y contents (0–7.8 at.%) were deposited by reactive magnetron sputtering to investigate the crystal structure, oxidation resistance, mechanical and tribological properties. A combination of X-ray diffraction (XRD), Raman spectroscopy and high resolution transmission electron microscopy (HRTEM) analyses showed that substitutional solid solution of Ti–Y–N is formed by substitution of Ti in TiN lattice by Y and all films exhibit a single-phase face-centered cubic (fcc) structure. The oxidation resistance temperature of Ti–Y–N films increased gradually from 560 °C at 0 at.% Y to 680 °C at 7.8 at.% Y. As Y was incorporated into TiN film, the hardness and elastic modulus of the films increased gradually from 21.7 GPa and 302 GPa at 2.9 at.% Y to 23.8 GPa and 316 GP at 7.8 at.% Y. The improvement of hardness was attributed to solid solution strengthening and fine-grain strengthening. Tribological properties of Ti–Y–N films performed using dry sliding friction and wear tests against Al2O3 depended on Y content to a large extent. The average friction coefficient and wear rate of Ti–Y–N films decreased from about 0.32 and 7.7 × 10− 7 m3/N·m at 2.9 at.% Y to about 0.20 and 6.8 × 10− 7 m3/N·m at 7.8 at.% Y. Optical microscope and Raman spectroscopy measurements revealed that the decreasing amount of tribo-film TiO2 and Y2O3 detected on the surface of the wear tracks could lead to the friction coefficient curve stay constant and decrease the friction coefficients. Moreover, the incorporation of Y into TiN matrix induced the films to undergo a transition from serve wear to mild wear.