Experimental study on hard turning of hardened tool steel with coated carbide cutting tools

Abstract

Hard turning is a technique that can be used to substitute grinding in the finishing operations for hardened steel (HRC 45 and above). However, the use of this technique was limited due to high cost of the cutting inserts. The introduction of newly developed carbide cutting tools has made hard turning more widespread. This study was undertaken to investigate the performance of KC 5010 which is a physical vapor deposition (PVD) titanium aluminium nitride (TiAlN) conventional geometry insert during finish hard turning of Stavax Electro-Slag-Refining (ESR) stainless tool steel (HRC 47 - 48). Various cutting speeds: 99.41, 130 and 170 m/min, and various feed rates: 0.098, 0.125 and 0.16mm/rev were employed. Turning was done under dry cutting condition and with constant depth of cut. Cutting forces, surface roughness and chip morphology were investigated. Results of surface roughness were satisfactory. Radial force seems to be the dominant force compared to the tangential force and feed force. Continuous chips were obtained regardless of the cutting conditions employed. Saw tooth chip formation was also found under high power microscope for all the cutting condition except at low cutting speed and feed. The radial force and surface roughness models were developed using the three level full factorial design. The mathematical models developed are statistically valid and sound, particularly for Fr and surface roughness. These are verified by the confirmation run experiments and therefore can be used for prediction within the limits of the factors investigated. Based on this research, hard turning with coated carbide inserts having conventional geometry performed satisfactory.