Grain orientation effects on the growth of short fatigue cracks in austenitic stainless steel

The influence of the grain orientation on short crack growth was studied in fatigued austenitic stainless steel (316L). Global and mesotexture were analysed using the electron backscattering diffraction (EBSD) technique in the scanning electron microscope (SEM). For two specimen types with and without preferred 〈1 0 0〉 oriented grains, respectively, the propagation rates of naturally grown short cracks were estimated. In both cases the damage evolution starts at grain boundaries, especially at twin boundaries, but is dominated later by transcrystalline propagating “TC”-cracks. Shorter fatigue life is correlated with a greater portion of TC-crack segments showing relatively high propagation rates. The expected acceleration of the crack propagation by plastic blunting/resharpening via double slip in a global texture with many 〈1 0 0〉 oriented grains of high slip symmetry will be overcompensated by small axial stresses within the elastically “weak” 〈1 0 0〉 grains. This agrees with the larger fatigue life of such specimens.