Tool life and surface integrity in turning titanium alloy

Titanium alloys have been classified as difficult-to-machine materials. Most of the information on the behaviour of titanium alloys and the mechanism involved at the tool-chip interface available are based on the observations taken during the commercial production of titanium components in the aerospace industry. In the present work, uncoated cemented carbide tools were used for the turning of Ti-6Al-2Sn-4Zr-6Mo. The experiments were carried out under dry cutting condition. The cutting speeds selected in the experiment were 100, 75, 60 and 45 m min(-1). The depth of cut was kept constant at 2.0 mm. The feed rates used in the experiment were 0.35 and 0.25 mm rev(-1). Two types of insert were used in the experiments. Tool wear was measured under optical microscope and tool life for machining titanium alloy of Ti-6246, has been recorded. The results have shown that the inserts with finer grain size have a longer tool life. SEM analysis has been carried out on the worn tools to determine the tools wear mechanisms. Majority of the tool failure mechanisms was due to flank face wear and excessive chipping on the flank edge. The paper also details some aspects of workpiece surface integrity following roughing operation. The surface of titanium alloy is easily damaged during machining operation due to their poor machinability. The machined surface experience microstructure alteration and increment in microhardness on the top white layer of the surface. Machined surfaces have shown severe plastic deformation and hardening after prolonged machining time with worn tools, especially when machining under dry cutting condition. (C) 2001 Published by Elsevier Science B.V.