Influences of Cutting Speed on Surface Roughness during Machining of Chromium Molybdenum Steel with Ceramic Insert Cutting Tool

Hard turning experiments using an Al2O3+TiC coated insert cutting tool for machining AISI 4140 chromium molybdenum steel bar for automotive industry applications were investigated. Turning experiments were carried out with varying cutting speeds ranging from 150 to 220 m/min under conventional dry hard operation. Analysis of variance showed that average surface roughness was significantly affected by cutting speed at the level of significance of 0.05. Average surface roughness value at a cutting speed of 220 m/min was lowest compared to average values at cutting speeds of 150 and 180 m/min, based on the least significant difference method. Micro-wear behaviors identified in the experiments through SEM micrographs consisted of edge chipping and micro abrasion on the Al2O3+TiC coated inserts.