3D X-ray tomography characterization of creep cavities in small-punch tested 316 stainless steels

Small-punch (SP) test has become an effective approach to evaluate creep properties of critical structural components in fusion and power plants for recent years. To explore the SP test technique, here we report quantitative analysis of creep cavities in the SP creep tested 316 stainless steel specimen at 600 °C and 500 N using a three dimensional X-ray tomography system. The results show that creep cavities nucleated preferentially at four kinds of places: high angle grain boundaries, intersection of twins and grain boundaries, triple junctions and intersections of first order and second order twins. The cavity morphology shows that both of the average size and the density of the cavities close to the fracture are the largest. The distribution of the local stress evaluated by the distribution of the cavities provides more details for an understanding of creep damage evolution in the 316 stainless steel at high temperature.