High speed cryogenic drilling of Ti-6Al-4V alloy under high pressure coolant conditions

Abstract

Titanium alloy (Ti-6Al-4V) plays a major role in aerospace and biomedical applications. Titanium alloys are drilled extensively to fabricate most of the aerospace structures. Ti alloys are having low thermal conductivity and are classified as difficult to cut material due to their high strength and adhesion toward the tool material. As a result, Ti alloys demand the use of coolant for drilling operations. Cryogenic is one of the most suitable methods of cooling as handling and disposal is easier compared to the wet and minimum quantity lubrication (MQL) methods. This paper deals with the high-speed drilling of Ti-6Al-4V alloy by the application of high-pressure cryogenic coolant at 22 bar. The results shows that there is a significant reduction in the thrust force ( FZ), torque ( MZ), and temperature ( T) and the effect of feed is negligible on circularity, cylindricity, and surface roughness of the holes when drilled at high speeds. The high pressure of the coolant helps in better penetration into the tool-chip interface and acts as an effective lubricant. This helps in reducing the friction between the tool and workpiece resulting in improved hole quality. These results are then compared with dry drilling of Ti-6Al-4V under same experimental conditions.