Study of characteristics of Cr2O3/CrN duplex coatings for aluminum die casting applications

Physical vapor deposition (PVD) coatings such as TiN and chromium nitride (CrN) have been successfully applied in metal forming industries for their excellent wear resistance. There has been interest in applying such coatings to the molding dies in order to reduce the coefficient of friction and extend die life. When applied to cast liquid Al and Al alloy into molded parts, die casting and injection molding technologies faced harsh conditions such as erosion, corrosion, creep and thermal fatigue. In this study, Cr2O3/CrN duplex coatings synthesized by PVD processes were evaluated for potential applications in molding dies. Cr2O3/CrN thin films of 3-μm thickness were deposited using cathodic-arc evaporation. By using X-ray diffraction, scanning electron microscopy, wear tests, TGA/DTA analysis and molten Al-alloy dipping tests, the performance of Cr2O3/CrN duplex coatings was investigated. The results demonstrated low frictional coefficient of Cr2O3/CrN thin films and oxidation resistance of 900 °C in ambient atmosphere. Due to low coefficient of friction, oxidation resistance and corrosion resistance in Al-alloy melt, Cr2O3/CrN duplex coating was promising for molding die applications.