AFM study of surface relief evolution in 316L steel fatigued at low and high temperatures

AbstractSurface relief of austenitic stainless 316L steel cycled with constant plastic strain amplitude at 93, 173 and 573 K to different early stages of fatigue life was studied using atomic force microscopy (AFM) and high resolution scanning electron microscopy (SEM–FEG). Characteristic features of surface relief topography and the evolution of persistent slip markings (PSMs) were documented for all temperatures. At 173 and 573 K PSMs consist of growing extrusions accompanied later by parallel intrusions while at the lowest temperature only static extrusions were found. In addition to distinct true PSMs fine slip markings with peakto-valley topography covering homogeneously different parts of grains and deformation induced martensite were detected in 316L steel fatigued at 93 K. Experimental results on the PSM topography and the kinetics of extrusion growth are discussed in relation to point defect models of surface relief formation leading to fatigue crack initiation