Characterization of Friction and Heat Partition Coefficients during Machining of a TiAl6V4 Titanium Alloy and a Cemented Carbide

Abstract

This article aims at characterizing the frictional behavior of a TiAl6V4 alloy and a carbide tool under extreme conditions corresponding to those occurring at the cutting tool–work material interface. A specially designed open tribometer was used to characterize the macroscopic friction coefficient, heat partition coefficient, and adhesion in the contact versus sliding velocity and contact pressure. It has been shown that titanium leads to intense adhesion, which seems to be even more intensive with high contact pressure and high sliding velocity, which limits the local sliding movement at the interface (stuck layer). However, the tribometer provides the evolution of an apparent friction coefficient and a macroscopic heat partition coefficient related to the shearing of titanium between the adhesive layer and the bulk material. An increase in sliding velocity or contact pressure induces a small decrease in the apparent friction coefficient as well as the heat partition coefficient. It has been shown that adhesion is thermally activated by a combination of contact pressure and sliding velocity, which leads to a threshold effect. Furthermore, the application of an emulsion showed a small decrease in the apparent friction coefficient associated to a decrease in adhesion. Finally, this work provides quantitative data on the apparent friction and heat partition coefficients versus sliding velocity and contact pressure that can support the development of macroscopic cutting models for titanium alloys.