Influence of membrane induced stress on internal stress of oxide film and substrate metal

Objective The purpose was to understand mechanical effects of crack tip film induced stress generated by oxide film on surface defects and stress corrosion cracking processes. Methods Taking nickel based alloy 600 as the research object, a finite element model of SCC full life cycle film induced stress was established, and influence of film induced stress on mechanical field of oxide film and matrix metal crack tip under different ΔT was obtained. Results Compressive stress generated within oxide film brought additional tensile stress to crack tip of substrate metal, which was film induced stress and accelerated rupture of oxide film. As temperature increased, film induced stress in both oxide film and substrate metal increased, but stress increase in oxide film was greater than that at the crack tip of substrate metal. At the interface between oxide film and substrate metal, both Mises stress and tensile stress exhibited a step phenomenon, which enhanced SCC sensitivity of crack tip. Conclusion The role of membrane induced stress in early stage of crack initiation couldn’t be ignored, it could cause membrane rupture and exposure of substrate metal, leading to nucleation and propagation of microcracks.