Mo–Ru coatings on tungsten carbide by direct current magnetron sputtering

Abstract

To extend lifetime and enhance the properties of the molding dies for glass molding, functional protective coatings have been applied on the core material with cost effectiveness during mass production. In this study, the Mo–Ru hard and protective coatings with the Ni interlayer were deposited on tungsten carbide substrate by direct current (DC) sputtering technique to improve the characteristics of molding die material. Intensive investigations on composition control through sputtering parameters were conducted. The surface hardness of the Mo–Ru films was measured by nanoindentation testing. In practice, the molding dies need to endure a thermal cycle of the temperature range from room temperature to around 600 °C. Under heat treatment at 600 °C for 4 h, the grain size was evaluated by X-ray diffractometry. It was demonstrated that the surface roughness, Ra, of Mo–Ru protective thin films was in the nanoscale through atomic force microscopy even under high temperature treatment. In addition, nanohardness test indicated that the annealed Mo–Ru films exhibited a high hardness over 11 GPa, which was compatible with those of the as-deposited films, and no significant degradation was revealed.