Tribological properties and oxidation resistance of (Cr,Al,Y)N and (Cr,Al,Si)N films synthesized by radio-frequency magnetron sputtering method

Quaternary (Cr,Al)N-based nitride was synthesized from alloy targets by the radio-frequency magnetron sputtering method. The mole fractions of (Cr,Al,Y)N were 44 mol% CrN, 52 mol% AlN and 4 mol% YN, while those of (Cr,Al,Si)N was 49 mol% CrN, 47 mol% AlN, and 4 mol% SiN. As-deposited (Cr,Al,Y)N and (Cr,Al,Si)N films had a cubic NaCl structure, and their average surface roughness Ra was approximately 8.1 nm and 6.3 nm, respectively. From thermogravimetric analyses, the weight of (Cr,Al,Y)N was observed to increase from 0.03 mg/cm2 to 0.30 mg/cm2 in the temperature range of 600 °C–1000 °C. In contrast, a linear increase in the mass gain of (Cr,Al,Si)N from 0.05 mg/cm2 to 0.18 mg/cm2 was observed up to a temperature of 1000 °C. Structural changes from single-phase cubic (NaCl) to wurtzite (AlN) and Cr2N occurred after thermal annealing in an ambient environment. During oxidation, metallic elements diffused toward the top surface, where the growth of oxides such as Cr2O3, Al2O3 and Y2O3 were confirmed. For the tribological test, the friction coefficient was below 0.6 under dry conditions at room temperature.