Wear evaluation of a self-propelled rotary tool when machining titanium alloy IMI 318

Abstract

This paper presents results of a self-propelled rotary tool (SPRT) tipped with round uncoated carbide (WC-Co) inserts in the finish turning of titanium alloy IMI 318. SPRT inserts exhibited superior wear resistance to conventional round and rhomboid-shaped carbides as well as to the rhomboid-shaped physical vapour deposition (PVD) TiN-coated carbide inserts owing to the distribution of the cutting energy along the entire tool edge. The SPRT-tipped inserts suppressed thermally related wear mechanisms at higher speeds beyond the capability of conventional tools. Chipping was the dominant failure mode of the SPRT inserts, resulting from cyclically fluctuating thermal and mechanical shocks induced by the continuous shifting of the cutting edge during machining. A fitted exponential wear model revealed that about 97 per cent of the average flank wear rate of SPRT inserts can be attributed to the joint effect of speed, feed and inclination angle, ε. Tool performance was improved by increasing the inclination angle ε which resulted in a lower machining temperature on account of a higher rotary speed and a lower relative cutting speed during machining. Lower component forces were recorded with SPRT inserts because of the reduced amount of work done in chip formation and lower friction at the rake face.