Journal of Materials Research and Technology (Jul 2023)
Machinability analysis of Ti-6Al-4V under cryogenic condition
Abstract
Aerospace alloys are termed as hard to cut materials owing to their low thermal conductivity, high temperature strength and elevated chemical reactivity. Cryogenic conditions can be effectively deployed to improve the machinability and productivity while addressing environmental and sustainability concerns connected with high tool wear and the use of conventional cutting fluids. Current work was undertaken to develop a novel tool wear map under cryogenic condition using cutting speed and feed rate as input variables. The developed map was demarcated into regions of low, moderate and high tool wear zones in addition to an unusually high wear zone, termed as avoidance zone existing between cutting speeds of 65–95 m/min and feed rates of 0.18–0.22 mm/rev. Characterization of developed map in terms of tool chip contact length revealed its direct relationship with cutting speed and feed rate accounting for the formation of different wear regions. Elemental analysis of avoidance zone detected high presence of TiN which results in larger tool chip contact length owing to its higher thermal conductivity. Chip morphology characterization highlighted an increase in chip compression ratio and decrease in shear angle due to the reduction of effective tool rake angle, further elevating the cutting zone temperature promoting wear. SEM and EDS spot analysis indicated the presence of adhesive and diffusion-dissolution wear mechanisms as the tool wear progresses. Comparative analysis with dry condition indicated that tool life is enhanced up to 100% using cryogenic media. Analysis of cryogenic tool wear map underscored the importance of careful choice of machining parameters in terms of increase in MRR up to 36% and tool life up to 58%. Overall, cryogenic tool wear map presents graphical interpretation of the machinability of Ti–6Al–4V in terms of tool wear.
