Thermal stability of TaN, CrTaN, TaSiN, and CrTaSiN hard coatings in oxygen-containing atmospheres

The feasibility of applying Ta-containing nitride protective coatings on glass molding dies was examined by conducting thermal cycling annealing. TaN, CrTaN, TaSiN, and CrTaSiN coatings are prepared by reactive co-sputtering. The thermal cycling annealing was performed at 270 °C and 600 °C in a 15-ppm O2-N2 atmosphere, a realistic glass molding atmosphere for mass production. This study investigated variations in crystalline structure, surface oxide scale, mechanical properties, surface roughness, and residual coating stress after thermal cycling annealing up to 2000 cycles. The results indicated that the near-amorphous Cr6Ta25Si11N58 coating exhibited a nanohardness of 19 GPa, a Young's modulus of 230-240 GPa, a surface roughness of 1 nm, and a consistent residual stress during the 2000 thermal cycles of annealing. The Cr6Ta25Si11N58 coating is proposed as an appropriate coating for molding glass.