Investigation of metal elements diffusion in Cr2O3 film and its effects on mechanical properties

Cr2O3 films were deposited on Inconel718 alloy substrate by using an arc ion planting system, and then annealed at 1000 degrees C in different atmospheres. The diffusion behavior of metallic elements from the substrate in different atmospheres and its effect on mechanical properties of the film were researched. The results show that Ti and Cr elements in the substrate would diffuse to Cr2O3 film surface when the films are annealed in argon, nitrogen and oxygen. A diffusion layer comprised of Cr and TiO2, which could attribute to the residual oxygen in furnace, formed on the surface of the argon-annealed film. In nitrogen atmosphere, Ti and Cr elements were nitrided to form Cr2N and TiN, and then they packed to form a diffusion layer on the film surface. Especially, a mesh-like heave comprised of Cr2O3 and Cr2Ti7O17 formed on the surface of the oxygen-annealed film. However, there is no element diffusion detected in the vacuum-annealed film, while lots of cracks formed on the film surface. Annealing in different atmospheres could improve the adherence strength obviously. The vacuum-annealed film maintains a high hardness, and possesses excellent tribological properties degradation. After argon and nitrogen annealing, the loose diffusion layers result in the hardness decreasing and tribological properties degradation. For the oxygen-annealed film, internal diffusion of oxygen decreases the surface hardness obviously. Moreover, although Cr2Ti7O17 lubricant formed on film surface, the loose surface structure deteriorates the tribological properties.