Creep behavior in austenitic stainless steel 316L(N): effects of minor element additions

The creep behaviour of 316 L(N) grade (reference steel) and a modified 316 L(N) grade with varying minor elements (N, Nb, B, C, etc.) (steel A) were compared. Creep tests at 575°C and 310 MPa was performed to assess the influence of these elements on precipitation and damage. The reference steel ruptured at 649 hours, while the steel A ruptured at 9203 hours. Metallurgical observations and damage analysis were conducted to explain these differences. Modifications in minor elements improved rupture time by influencing both primary and tertiary creep stages, resulting in superior performance. MX precipitates, promoted by increased Nb and N content, delayed M23C6 nucleation, which typically serves as a site for creep cavity formation. This led to different cavity and crack formations between the steels: wedge-type for the reference steel and R-type for the steel A, explaining the improved creep resistance in the steel A.