Microstructural evaluation of sputtered Ru–Pt multilayer anti-stick coatings for glass molding

This work describes the performance of multilayer Ru–Pt coatings with Ti as the interlayer deposited on graphite substrate for applications in precision glass molding (PGM). Different from the previous evaluations with other kinds of coatings for PGM temperatures below 650 °C, we studied the anti-sticking behavior of the developed coatings by annealing them at 750 °C with aluminosilicate glass coverage in a rough vacuum environment. Glass adhesion was not observed even after 40-hour annealing suggesting the high chemical inertness of the coatings at the high temperature. In addition, the Ru–Pt multilayer coatings exhibited a better anti-sticking property than monolayer (Ru or Pt) coatings. The microstructure, surface morphology, and hardness were further characterized. High-resolution transmission electron microscopy (HRTEM) analysis confirmed the perseverance of layered structure after annealing at 750 °C and the hindrance effect on dislocation motion and diffusion arising from the Ru-Pt interfaces. After long-term annealing, interdiffusion leads to Pt-Ru solid solutions, which further enhance the mechanical performance and stability of the noble metal coatings, beneficial for prolonging the lifespan of PGM molds and the optical quality of molded glass. The high anti-sticking and mechanical performances of the developed coatings were finally confirmed in industrial tests.