Wear Pattern of Coated Carbide Tools in High Speed Threading of a Ni-Cr-Mo Base Steel

摘要

PVD TiN and A1_2O_3 coated tools with P20-P30 and K05-K20 substrates respectively were used to perform an external right hand thread cutting operation on a Ni-Cr-Mo base steel up to a cutting speed and feed rate of 225 m min~(-1) and 0.44 mm rev~(-1) respectively. The feed rate had greater influence on tool life followed by cutting speed and finally the depth of cut. A parabolic shape wear pattern with adhering flake-like oxide debris was found to be consistent on the worn TiN coated tools while the Al_2O_3 coated tools showed little or no adhering debris and wears in a pattern similar in shape to a right cone. Although the test results show that cutting speed and feed rate had the most significant influence on tool life, the wear pattern along the nose region of the tool face was found to have functional correlation between the tool life, wear volume, flank wear rate and cutting forces. The feed forces were generally very small and did not show any significant effect on tool performance. The TiN coated tools with sharp edges gave lower tool life and were more susceptible to higher flank wear rate, wear volume and cutting forces than the Al_2O_3 coated tools with honed edges. The better performance of the Al_2O_3 coated tools was attributed to the composition of the substrate and improved mechanical and tribological properties of the coating materials.