Stress corrosion cracking characteristics of CF8A austenitic stainless steels and interactions between multiple cracks in a simulated PWR environment

Abstract

The stress corrosion cracking behaviors of CF8A austenitic stainless steels in a simulated pressurized water reactor environment are systematically investigated by slow-strain-rate tensile tests. Numerous transgranular stress corrosion cracking (TGSCC) cracks are identified upon the fracture of CF8A austenitic stainless steel surfaces. The specimens tested at lower strain rates showed higher fractions of TGSCC, a larger number of cracks, and smaller crack opening displacement. These phenomena are caused by anodic dissolution and crack interactions. The anodic dissolution is dominant at lower strain rates, and thus the crack-tip morphologies are changed by the diffusion of metal atoms and micro-pores. The crack interactions increase rapidly with increasing number of cracks and decrease of the crack-tip radius and crack spacing ratio. In addition, the inhomogeneity of the growth of interaction cracks results in the small cracks being shielded by the preferred growth cracks. On the contrary, the main cracks are accelerated by the stagnation of small cracks, eventually becoming critical cracks that lead to specimen fracture.