Low cycle fatigue properties of an austenitic stainless steel 316L processed by surface mechanical attrition treatment

Abstract

International audienceEffect of surface mechanical attrition treatment (SMAT) on low cycle fatigue properties of an austenitic stainless steel 316L is studied using cyclic push-pull loading tests, with total strain amplitudes of ±0.5%, ±0.8%, and ±1.25%, respectively. Based on Electron Backscatter Diffraction (EBSD) observation and microhardness test, nanocrystalline layer, mixed grain size layer, and work hardened layer were generated near the treated surface by SMAT. During cyclic loading, SMAT-processed material exhibits higher cyclic stress amplitude due to the higher strength of SMAT affected region. Scanning Electron Microscopy (SEM) observation of fatigue fracture indicates that fatigue crack initiation occurs likely on external surface of SMAT-processed material, and propagated inward in transgranular mode with the formation of fatigue striations. Furthermore, fatigue lifetime of material under high strain amplitude (±1.25%) decreases due to SMAT. Fatigue Life analysis using Coffin-Manson law and energy dissipation theory indicates that this lifetime decrease is considered to be due to the diminution of ductility and fatigue damage capacity, along with higher energy dissipation rate in the SMAT affected region