HARD TURNING PERFORMANCE EVALUATION USING CVD AND PVD COATED CARBIDE TOOLS: A COMPARATIVE STUDY

This study emphasizes the comparative cutting performance evaluation of CVD- and PVD-coated carbide inserts in hard turning of AISI D2 steel. The cutting factors, namely cutting speed (100m/min), tool feed rate (0.08mm/rev), and depth of cut 0.2mm, have been fixed for the entire study. The comparative study is based on the analysis of the obtained test results of flank wear, tool life, auxiliary flank wear, surface roughness, and surface texture. Both tools are catastrophically failed when tool wear reached limiting flank wear (VBc=0.3mm) criteria. SEM and EDS analysis of both the tools (at their end of tool life) are carried. Diffusion followed by adhesion is found to be the prime mechanism at the end of tool life. Based on limiting flank wear criteria, the tool life of CVD and PVD tools was estimated as 65 and 57min, respectively, i.e. the tool life of the CVD tool is 14% longer than that of the PVD tool. Considering the limiting criteria of surface roughness (Ra=1.6μm), the tool life of the CVD tool was estimated as 63min while for the PVD tool, it was found as 54min i.e. about 14.3% higher tool life was found for the CVD tool relative to the PVD tool. The auxiliary flank wear was observed to be lower for the CVD tool relative to the PVD tool. Surface roughness for both the tools increased with cutting time and the relatively larger rough surface was obtained with the PVD tool. The machining cost of one pass of the CVD tool is 2.5% less than that of the PVD tool. However, for mass production, the CVD tool is more efficient than the PVD tool for machining hard D2 steel (57±1 HRC).