Experimental evaluation of multilayered CVD- and PVD-coated carbide turning inserts in severe machining of AISI-4340 steel alloy

This manuscript addresses the machining performance between multilayered PVD- & CVD-coated-carbide inserts in severe dry turning of AISI-4340 alloy. Three machining factors and three-level factorial experimental patterns (by Taguchi's L-9 OA method) were applied here. The analytical investigation of the variance was applied for each experiment for the purpose of studying the impact of these cutting factors on turning inserts. Flank wear of the tool was estimated using the optical microscope & surface roughness was determined in terms of R-a factor by using mobile roughness tester. The obtained experimental results revealed that, for surface roughness the feed rate was found more significant factor followed by cutting speed on both coated-carbide tools. However, for flank wear the cutting velocity was found more significant, followed by feed rate on both coated-carbide tools. A better surface finish was observed on PVD-coated insert at low and medium velocities; but, with the increasing speed the CVD-coated tool shows better surface smoothness. The obtained results also confirmed that more mechanical wear occurs on the PVD-coated insert with compared to CVD-coated insert when operating under the same cutting and environmental conditions. Thus, under higher machining velocity, the CVD-coated insert has shown less wear with compared to PVD-coated tool during high load turning process, due to which it is generally more preferred for practical applications.