STUDY OF TOOL TEMPERATURES, FORCES - AND CHIP FORMATION IN MACHINING TITAN-31

Abstract

TITAN-31 (Titanium alloy, Ti-6A1-4V) i.s widely used for aerogas turbine engines because of its attractive property of highstrength to weight 'ratio. But TITAN-31 is generally regarded as difficult to machine material because of high temperatures in cutting zone, due to their low thermal conductivity and strong adhesion between tool and work material resulting from their high chemical reactivity. Most of tool materials, as diamond and cubic boron nitride are highly reactive with titan-31 at speeds above 100 m/min and consequently are not used. With--high speed steel tools the cutting speed hardly exceeds 19 m/min, when machining titanium base alloys. Machining industries are continuously demanding for higher production rate and machinability. Higher production rate can be achieved at high cutting speeds and feed rate which is associated with generation of very 'high cutting temperature, rapid tool wear and large cutting forces and stresses. However, coated carbide tools are said to reduce the cutting forces and improve wear resistance. But not much work is available in the literature. Recently multicoated tools have also been developed. The work has, therefore, been undertaken to evaluate the performances of currently available grades of coated and uncoated carbides in machining titan-31. The performance of a multicoated insert WIDALON TK15, single layer coated carbide insert TG, having positive rake iii angle and negative rake angle has been studied w.r.t. cutting temperatures and forces under different cutting conditions. For comparison, uncoated carbide TTX and TH-20 have been used. The mechanism of chip formation has also been studied. The results show that WIDALON TR15 multilayer insert gives a better performance under high speed cutting conditions [77-100 m/min] followed by a TiC coated insert TG having negative rake angle. The uncoated insert TTX gives good performance at lower cutting speed [ 48 m/min]. The uncoated carbide, and coated carbide inserts with positive rake angle usually fail by breakage at the nose radius region [> 48-m/min, for feed rate range 0.12-0.16 mm/rev].