Creep Damage Evolution in 316L Stainless Steel: Correlating Cavitation with Acoustic Emission

This study investigates the creep deformation characteristics of conventionally manufactured 316L stainless steel at an elevated temperature of 650°C, assessed under three distinct quasistatic stress levels (241 MPa, 282 MPa, and 311 MPa). The investigation is particularly focused on the progression of damage within the diffuse necking region, an antecedent to catastrophic rupture. A comprehensive post-mortem microstructural analysis, utilizing the precision of scanning electron microscopy (SEM), was conducted to thoroughly evaluate the morphology and distribution of creep-induced defects, including pores, grain boundary cracks, and intergranular voids. In parallel, the application of real-time acoustic emission (AE) sensing was employed to detect and analyse the elastic wave activity generated by microstructural failure phenomena and creep stages. Through the adept integration of statistical analysis of microstructural defects with sophisticated AE signal interpretation, the study elucidates a strong correlation between the applied stress levels and the trajectory of damage evolution. At the lower stress level (241 MPa), fewer but significantly coarser voids were observed, whereas at the higher stress level (311 MPa), numerous localised microcracks formed with limited coalescence. This dual characterization approach effectively links dynamic AE signatures to the underlying damage mechanisms, thereby crucially addressing a significant gap in the real-time assessment of creep degradation in stainless steels. The resulting findings enhance the predictive capability of material degradation and support advanced structural health monitoring strategies for high-temperature applications, particularly within the scope of Generation IV nuclear reactor components