Thermal ageing and creep damage in 316L(N) alloys: a 3D analysis

Creep behaviour of two alloys, namely, classical 316 L(N), labelled as LN, and nitrogen-modified 316 L(N), labelled as an HN, in this present work, have been studied at 575 °C at a stress level of 310 MPa. 3D analyses have been done by using two different X-ray sources. Additions of nitrogen in 316 L(N) have been demonstrated to be beneficial for extending the life of austenitic stainless steels, decreasing the creep damage. Creep cavities have been classified based on their shape, and the growth orientation of cavities is analysed. Even though the total lifetime of LN sample is shorter (649 h) compared to HN (9203 h), it exhibits more cavities. The orientation of the cavities and the complex shape of cavities have been proving that stress direction has a huge effect on the LN sample damage development with a concentration of 10° and 90°.