Chemical inertness of Ta–Si–N coatings in glass molding

Abstract

Glass molding can be employed to fabricate high-quality lenses with a lower cost and higher process rate than those of the traditional glass lens production method. Glass molding is widely employed in manufacturing precision optical elements with aspheric surfaces. In this study, amorphous Ta–Si–N coatings with a Ti interlayer were sputtered on cemented carbide substrates to evaluate their potential as protective coatings on glass molding dies. Commercial moldable SiO2–B2O3–BaO-based and B2O3–ZnO–La2O3-based glasses were used to evaluate the chemical inertness of Ta–Si–N coatings in glass molding. Thermal cycle annealing, which involves annealing at 270°C and 600°C and maintaining the glasses at 600°C±10°C for 1min/cycle, was conducted in a quartz tube furnace to simulate glass molding in a continuous flow of a 15-ppm O2–N2 atmosphere. The glass and coating assemblies were subjected to up to 1000 thermal cycles. The variations in the crystalline structure and surface roughness after various annealing durations were investigated.