Machining behaviour of Ti-6Al-4V and Ti-5553 alloys in interrupted cutting with PVD coated cemented carbide

Abstract

Machining behaviour of Ti-5553, Ti-6Al-4 V mill-annealed (MA) and Ti-6Al-4 V solution treated and aged (STA) alloys was studied in different interrupted cutting operations using PVD coated cemented carbide tools. Single tooth face milling was employed to study the wear behaviour and tool life of the coated tools that were further inspected using scanning electron microscopy. The results indicated that a poor machinability was observed for Ti-5553 when compared to Ti-6Al-4 V (STA) and Ti6Al-4 V (MA). This was found to correlate reasonably well with an increase of work material adhesion severity on the cutting tool that resulted in an increased chipping and led to catastrophic tool failure. Series of orthogonal interrupted cutting tests were performed subsequently to investigate the role of work material and cutting data on the chip formation, mechanical loads and frictional conditions at the tool-chip contact. A detailed analysis of the chip segmentation characteristics of the different Ti alloys is provided and the results are employed in different analytical models to assess the shear strain, strain rate and segmentation frequency. Finally, a comparison of Ti-5553 and Ti-6-4 (MA) in interrupted turning is presented where the differences in terms of cutting temperature are discussed.