Microstructure, mechanical and tribological properties of the nc-Cr _xC _y/a-C and nc-Cr _xC _y/a-C:H nanocomposite coatings on oxygen-hardened Ti-6Al-4V alloy (Conference Paper

摘要

The nanocomposite coatings, nc-Cr _xC _y/a-C and nc-Cr _xC _y/a-C:H, consisting of chromium carbide nanocrystals embedded in an amorphous hydrogen free carbon (a-C) matrix or in an amorphous hydrogenated carbon (a-C:H) matrix deposited on oxygen-hardened Ti-6Al-4V alloy by magnetron sputtering were investigated. Oxygen hardening of titanium alloy was performed by oxidation under plasma glow discharge. For both coatings, the phase identification by high-resolution transmission electron microscopy revealed the presence of Cr _7C _3 and Cr _(23)C _6 nanocrystals of size 2?·13 nm embedded in an amorphous carbon a-C and a-C:H matrix. The microhardness values were found to be 9.7 GPa and 12.1 GPa for the nc-Cr _xC _y/a-C and nc-Cr _xC _y/a-C:H coatings, respectively, and 10.6 GPa for oxygen-hardened titanium alloy. Scratch tests indicated good coating-substrate adhesion for both coatings. It was found that the hydrogenated nc-Cr _xC _y/a-C:H coating exhibited lower coefficient of friction ranging from 0.1 to 0.15 (while sliding 1-mm diameter alumina ball) as compared to friction coefficient of nc-Cr _xC _y/a-C coating which showed higher value, up to 0.2. The coated alloy features much better wear resistance than oxygen-hardened one.