Influence of surface morphology on the fatigue behavior of metastable austenitic steel

Using a low temperature turning process with carbon dioxide cooling in the cutting zone a variation of the morphology at the specimen surfaces of the metastable austenitic steel AISI 347 was realized. In LCF and HCF fatigue tests at ambient temperature and 300 degrees C the influence of the surface morphology on the cyclic deformation behavior and fatigue life was investigated by the measurement of stress-strain hysteresis. An additional magnetic measurement allows the characterization of the phase transformation from paramagnetic austenite in ferromagnetic alpha'-martensite during the turning processes and during cyclic loading. The surface morphology was studied in detail by SEM and x-ray investigations.