Characterization of friction coefficient for simulating drilling contact for titanium TiAl6V4 alloy

This paper deals with the characterization of friction during drilling of a titanium alloy. After a review on friction models in drilling, a sensitivity study to sliding speed, contact pressure, lubrication and tool coatings is presented. A dedicated tribometer has been used and highlighted that titanium is significantly influenced by sliding velocity and contact pressure, whereas lubrication and coating have a minimal effect on friction. The paper then questions whether friction is similar on a drill's rake/flank faces and on its margins. It is pointed out that tribological conditions on the margins are completely different compared to the ones on the rake and flank faces. Whereas friction on both rake and flank faces is considered as an open tribosystem, friction on the margins corresponds to a closed tribosystem configuration. It is shown that there is a large variation in friction between both tribosystems, and that the closed tribosystem on the margins leads to a significant drift over time. Finally, this paper shows that modelling of friction around a drill is complex and necessitates the separate study of both the rake/flank faces and the margins. (C) 2020 CIRP.