Effects on the deformation-induced martensitic transformation in AISI 304 in external longitudinal turning

During the turning process of metastable austenitic steels, austenite is transformed into hard martensite by plastic deformation at low temperatures. This enables the production of components, which have both a hardened subsurface zone and a ductile core. Cryogenic cooling allows the subsurface zone to be hardened during machining, which leads to a shortening of the process chain. However, effects such as wear can make it challenging to adjust the properties of the subsurface zone during turning. By adjusting the tool microgeometry with a flank face modification, the wear condition can be kept constant for a certain period. In addition, the significance analysis with different tool microgeometries shows that only feed and initial temperature have a significant effect on the martensite formation.