The effect of Titanium Alloy Composition and Tool Coating on Drilling Machinability

Abstract

Excessive tool wear and poor machinability is observed in the machining of high strength, near-β titanium alloys when compared to α + β titanium alloys such as Ti-64. Tooling suppliers want to better understand drilling machinability in terms of (1) why alloy composition influences tool wear behaviour, (2) how this impacts part integrity and (3) the effectiveness of tool coating. This paper presents a novel approach to investigating the mechanisms by which tool wear and microstructural deformation occur in a range of titanium alloys, through the manipulation of the force experienced by the tool and work piece. The investigation compares and contrasts the drilling machinability of three important aerospace titanium alloys. Force feedback, tool wear and microstructural damage results highlight key differences when drilling different titanium alloys. Such findings will contribute to tool design, providing a better understanding of wear and machinability in near-β titanium alloy drilling.