X-ray fractography studies on austenitic stainless steels

In this investigation, the fracture surfaces of SS 304 and SS 316 austenitic steels were analysed using the X-ray fractography technique. In both cases, a decrease in the austenite content was observed at the fracture surface as a result of deformation induced martensite, indicating a linear relation with Kmax within the stable crack growth region. The presence of this martensite was found to be confined to a very thin layer close to the fracture surface. The magnitudes of the residual stress (¿r) as well as the profile breadth (B) as a function of Kmax in martensite were found to be higher than in austenite, with greater differences in SS 304 than in SS 316. In both the steels a gradual decrease of ¿r with depth below the fracture surface was noticed. While a gradual decrease of B was noticed in SS 304, a shallow minimum was noticed at a depth of about 100 ¿m in SS 316.