Stress Corrosion Cracking Behavior of 300M Steel under Different Heat Treated Conditions

Abstract

The resistance of 300M steel to stress corrosion cracking in a 3.5% NaCl solution was studied as a function of heat treatment. Threshold stress intensity was affected by microstructural features, including prior austenite grain size, amounts of retained austenite, and twins, in addition to grain boundary segregation and fracture toughness of the steel. Crack growth rate was also dependent on microstructure and segregation, but the number of constraint points exerted the maximum influence. The effect of a modified heat treatment, which has been shown to improve all investigated mechanical properties to a significant extent, upon stress corrosion cracking (SCC) properties, was also studied. This heat treatment resulted in significantly higher threshold stress intensity and lower crack growth rate. The results are discussed in terms of microstructure and fractography.