Machinability and Surface Quality Issues in Finish Turning of Hardened Steel with Coated Carbide and CBN Tools

The objective of this article was to investigate the performance of coated carbide and low content cubic boron nitride (CBN-L) tools in finish turning of hardened steel. The tool life, cutting tool temperature, cutting forces, and surface integrity of machined workpiece achieved with both the tools under similar cutting conditions were compared. The effect of variation in cutting conditions on the performance of coated carbide and CBN inserts was also analyzed. With the selected flank wear criterion of VBmax = 200 mu m, significant advantage in terms of optimum surface integrity was observed. The performance of coated carbide tools deteriorated at highest cutting speed tested, and significant chipping/breakage of the cutting edge was observed. The tool wear affected the cutting zone temperature, as well as residual stress generated on the machined surface.