Effects of thermal aging on the stress corrosion cracking behavior of cast stainless steel with different δ-ferrite levels in high temperature water environment

This study focused on the combined effect of ferrite content and thermal aging on the stress corrosion cracking (SCC) of CF8A by using an alternating current potential drop (ACPD) technique to measure the SCC growth rates in high temperature water environment. The results show that thermal aging and high δ-ferrite content increased the susceptibility to SCC. The SCC susceptibility to the factor of δ-ferrite content of CF8A is greater than that for thermal aging treatment. Furthermore, the SCC mechanisms at the crack tip were investigated using transmission electron microscopy (TEM). The formation of Fe oxide ahead of the crack tip enhanced the crack propagation along γ / δ-ferrite interface. For the specimen with high δ-ferrite content, the δ-ferrites were distributed in continuous networks, which provide continuous SCC-sensitive paths.