Influence of dimple and spot-texturing of HSS cutting tool on machining of Ti-6Al-4V

Abstract

Machining of titanium alloys using high speed steel (HSS) tools is difficult due to their lower thermal conductivity which increases temperature of the HSS cutting tools thus accelerating their wear. Texturing on rake face of a cutting tool has recently emerged as a promising and environment friendly method enhancing removal of heat from the machining zone. This paper reports study on influence of spot and dimple textures by micro-plasma transferred arc powder deposition (μ-PTAPD) process on rake face of the HSS cutting tools. Experiments were conducted to study effects of μ-plasma power, powder flow rate and exposure time on dilution of spot-textures by making spots of Stellite powder on the HSS tool and to identify their optimum values for making an array of spots on rake face of the HSS tool. Similarly, effects of μ-plasma power and exposure time on diameter, depth, and aspect ratio of dimples were studied to identify their optimum values for producing an array of dimples on rake face of the HSS tool. Spot-textured, dimple-textured, and non-textured HSS tools were used in turning of Ti-6Al-4 V alloy and their performance was compared in terms of machining forces, flank wear, tool temperature, chip shapes, and surface roughness of the turned workpiece. Use of spot-textured HSS tool resulted in least values of cutting and thrust forces, chip-tool contact length, tool temperature, flank wear, adhesion of the workpiece material to the tool, and average surface roughness of the turned workpiece than the dimple-textured and non-textured HSS tools at different cutting speeds. Performance of the dimple-textured HSS tool was better than the non-textured tool in these aspects. Spots helped in formation of segmented chips by reducing curling radius of chips whereas non-textured and dimple-textured tools formed continuously curling ribbon-like chips. Spots also act as fins which enhance heat loss to the machining environment and helping in reduction of tool temperature. This study proves that spot-texturing of rake face of HSS tool by μ-PTAPD process is an economical, effective and environment friendly method to improve machining of titanium alloys. © 2018 Elsevier B.V.