Effects of Copper and Sulfur Additions on Machinability Behavior of High Performance Austenitic Stainless Steel

Flank wear, cutting force, the number and area of sulfides, and shear strain rate were measured to elucidate the synergistic effects of Cu and S additions on machinability of high-performance austenitic stainless steels with a basic composition of Fe-18 %Cr-21 %Ni-3.2 %Mo-1.6 %W-0.2 %N. As Cu and S content increased, flank wear and cutting force decreased. While Cu and S content increased, shear strain rate and shear angle increased. The tool life for an alloy with 3.1 %Cu + 0.091 %S was about four times longer than that of an alloy with 0.06 %Cu + 0.005 %S due to high shear strain rate generated by Cu addition, lubricating films of ductile (Mn, Cr)S sulfides adhering to tool surface and low cutting force resulting from thinly and lengthily continuous sulfides formed in chips during machining.