Defect-free high-feed milling of Ti-6Al-4V alloy via a combination of cutting and wiper inserts

Abstract

Ti-6Al-4V alloy machining is challenging due to inherent properties. Wiper inserts improve the surface finish at higher feed rates because of multi-radii geometry. Wiper inserts when combined with the cutting inserts can provide smooth surface finish. The current work is aimed to study the influence of cutting and wiper inserts in Ti-6Al-4V alloy milling while considering wear scar of tool/life, surface roughness, surface topography, micro-hardness, and microstructural evaluations as output responses under higher levels of feed rates in dry machining. The combination of cutting insert along with wiper geometry provides machining innovation due to the fact that good surface finish can be achieved in a single step. Three levels of feed rate (f) (1.2, 1.4, 1.6 mm/revolution) along with three levels of depth of cut (ap) (0.25, 0.40, 0.50 mm) were employed for the experimentation. The variation in workpiece surface roughness (Ra) was found in between 0.3 and 0.71 μm-Ra. Surface topography analysis under the scanning electron microscope (SEM) of the machined specimen revealed no voids/cracks; however, scratch marks/welding of microchips were noticed. No alteration in microstructure was found when milling at 1.2 and 1.4 mm/revolution feed rate. A white layer deepened to 18 μm from the milled surface was seen at a feed rate of 1.6 mm/revolution. In addition, approximately 15% increase in micro-hardness was observed beneath the milled surface when evaluated machining variables were at their peak levels, i.e., at 1.6 mm/revolution and 0.5 mm respectively, while only 5.4% increase in the said response was observed at f of 1.2 mm/revolution.