Thermal stability of Ir–Re coatings annealed in oxygen-containing atmospheres

Ir–Re coatings are widely applied as protective coatings on glass molding dies. Because the glass molding process in mass production is conducted in an oxygen-containing atmosphere at a high temperature, the protective coatings must endure cyclic annealing treatments. Oxidation and thermal stability of Ir–Re coatings has received scant attention. In this study, Ir–Re coatings were prepared using co-sputtering. Constant-temperature annealing treatments were conducted at 600 °C under a 1% O2–Ar atmosphere, which is an oxidation-accelerating atmosphere. The thermal cyclic test was performed at 270 and 600 °C under atmospheres of 1% O2–Ar and 15 ppm O2–N2, respectively. The 15 ppm O2–N2 atmosphere is glass molding atmosphere suitable for mass production. The variations in crystalline structure, nanohardness, surface roughness, and residual stress after various annealing treatments were investigated. The more elevated Ir content coating, namely, Ir0.77Re0.23, displays superior thermal stability compared with the lower Ir content coating, namely, Ir0.53Re0.47.