Friction and wear properties of amorphous and nanocrystalline Ta-Ag films at elevated temperatures as function of working pressure

Abstract

Ta-Ag immiscible alloy film shows potential application as a protective coating during sliding contact at high temperatures. In this study, Ta-Ag films were deposited on carbon steel by DC magnetron sputtering at the ambient temperature. The microstructures of Ta-Ag films were adjusted by controlling working pressures (0.2–0.8 Pa) and sputtering powers of tantalum (90 W–100 W). The nano-crystalline α-Ta is deposited at the working pressure of 0.2 and 0.4 Pa while the amorphous Ta is produced at 0.6 and 0.8 Pa for Ta90-Ag8 films. The hardness and elastic of Ta-Ag films decreases with the increase of sputtering pressure. The friction coefficients of nanocrystalline Ta90-Ag8 films deposited at 0.2 and 0.4 Pa are lower than that of amorphous films deposited at 0.6 and 0.8 Pa from RT to 600 °C. A friction coefficient of about 0.32 and low wear rate (1.6 × 10−5 mm3/Nm) is obtained for the Ta90-Ag8 film deposited at 0.2 Pa at 700 °C.