A STUDY OF THE MACHINING OF CAST AUSTENITIC STAINLESS-STEELS WITH CARBIDE TOOLS

The relative performance of coated and uncoated carbide tools (inserts) in the machining of three cast austenitic stainless-steels has been assessed with reference to cutting-force requirements (both P-x and P-z), tool rake-face wear and chip characteristics. One of the experimental steels conformed approximately to CF8M grade, whilst the compositions of the other two steels were modified by micro-alloying with nitrogen and by varying the percentage of other alloying elements. All the tools were of identical size and geometry. The cutting forces required for turning the jobs with titanium-nitride coated carbide tools were consistently greater than those for uncoated tools. Deep rake-face craters formed on the coated tools by diffusion wear even during short machining runs. Evidence of built-up-edge formation was detected also. The compositions of the steels influenced their machinability. However, further work will be necessary to identify the exact effect of nitrogen on the machinability of these cast stainless steels.