Microstructural variations in 316L austenitic stainless steel and their influence on tool wear in machining

The aim of the present study was to investigate how variations in the microstructure of 316L austenitic stainless steel influence the tool wear during machining. A detailed comparison between two workpieces of 316L, supplied by different producers was made regarding their microstructures and the resulting tool wear during machining. Machining the two workpieces resulted in distinctively different tool wear responses. During the tool life tests, machining one of the workpieces resulted in a steady increase in tool flank wear and the criterion of maximum flank wear land was reached after about 15 and 5 min at low and high cutting speed respectively. However, no significant flank wear was observed when machining the other workpiece under the same cutting conditions. Post-test characterization of the worn tool surfaces showed that tool wear by dissolution/diffusion were the main wear mechanisms for cutting both workpieces. The distinct differences in tool wear progression were linked to varying micro-constituents present in the two workpieces. Specifically, the main factor controlling the wear was attributed to differences in the composition of oxide inclusions. In the one workpiece's case, the specific composition and hence mechanical properties of the inclusions gave rise to a stable protective layer covering the tool surface. During cutting, this inclusion layer was acting as a diffusion barrier, thereby suppressing tool wear by dissolution and hence limiting the progression of flank wear. In contrast, the characteristics of the oxide inclusions present in the other workpiece did not favor the formation of a protective layer on the cutting tool surfaces.