Deep rolling of austenitic steel AISI 304 at different temperatures - near surface microstructures and fatigue

In metastable austenitic stainless steels the formation of high dislocation densities, compressive residual stress states, strain-induced martensite and nanocrystalline regions are the most important consequences of mechanical surface treatments leading to retarded fatigue crack initiation as well as propagation. These properties can be altered in a characteristic way applying different deep rolling temperatures. he main objective of this paper is to clarify the role of the different near surface microstructures introduced by deep rolling operations on the fatigue behaviour of steel AISI 304 especially in the low cycle fatigue region. For this purpose special experimental techniques were applied allowing deep rolling operations in the temperature range between - 192 degrees C and + 700 degrees C. Results clearly show that the amount of strain induced martensite by deep rolling in near surface layers is less important than the stability of the microstructures under fatigue loading.