Evaluation of the wear mechanisms and surface parameters when machining internal combustion engine valve seats using PCBN tools

This research aims to investigate the influence of cutting speed (vc), depth of cut (doc) and feed rate (f) on the machining of valve seats of internal combustion engines using polycrystalline cubic boron nitride (PCBN) tools. The workpiece material was Fe–C–Cu–Ni–Mo alloy obtained from powder metallurgy technique. The quality of the resulting surface is fundamental for the performance of engines and was estimated by Ra, Rq, Rz, Rt and Wt surface roughness parameters, while relations between surface and cutting parameters were performed. Among the cutting parameters the cutting speed was the most influent on the wear of the tools. The predominant types of wear were flank and crater, while mechanisms as attrition prevailed at low vc and diffusion at medium vc. The dynamic instability identified by accelerometers at the machine was decisive in leading to discontinuous chip flow and chipping phenomena due to low fracture toughness of tool material.