High temperature performance of silver coating deposited by magnetron sputtering

Abstract

Silver coatings were deposited on nickel-based super-alloy by medium-frequency and direct-current magnetron sputtering and electroplating. The oxidation kinetics, microstructure, phase composition, and surface roughness (Ra) of coatings were characterised by SEM, EDS, XRD, and CLSM. The tribological behaviour was evaluated by a wear tester. The results showed that the high-temperature oxidation resistance of both coatings was similar: the mass gain (ΔMG) at 400°C was less than 0.05 mg/cm2; ΔMG at 650°C both conformed to the parabolic law. After holding at 25°C, 200°C, and 400°C, Ra(MS) were 1.062, 0.940, and 1.234 μm, Ra(EP) were 1.370, 1.461, and 1.584 μm. At the increasing temperature, the coefficient of friction (COF) of the MS coating decreased, with the value of 0.66, 0.55, and 0.43 corresponding to 25°C, 200°C, and 400°C, respectively. However, due to the obvious adhesion effect, COF(EP) changed inversely, which were 0.56, 0.62, and 0.75, respectively.