ON THE TOOL-LIFE EQUATION OF TIN-COATED HIGH-SPEED STEEL TOOLS

The introduction of computer numerical control and direct numerical control has demanded the precise prediction of tool-life under known constant cutting conditions. The recent developments in TiN coating technology have made conventional high speed steel (HSS) tools more versatile. Efforts are made to understand the behaviour of TiN coats 5-mu-m thick on the performance of turning tools. Two types of cutting tools were used to turn C15 low carbon steel workpieces. They are conventional M42 HSS and the other TiN-coated M42 HSS tools. The coating was accomplished by physical vapour deposition (PVD) using the plasma arc evaporation technique. A conventional HSS tool was used as a benchmark. A stepwise multiple regression analysis was used to investigate the combined effect of speed and feed on tool-life. This is found to have more effect on the tool-life equation of TiN-coated HSS tools. The tool-life of TiN-coated tools was found to be from 3 to 10 times higher than the conventional HSS tool under all cutting conditions. The results revealed that a second-order model is more appropriate for the mathematical modelling of cutting data for TiN-coated tools.