Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014)
    Thin Films Wednesday Sessions
       Session TF-WeP

Paper TF-WeP40
High Temperature Self-Lubricant Coatings with Release of a Lubricious Agent for Machining Applications

Wednesday, December 10, 2014, 4:00 pm, Room Mauka

Session: Thin Films Poster Session
Presenter: Albano Cavaleiro, University of Coimbra, Portugal
Authors: F. Fernandes, University of Coimbra, Portugal
T. Polcar, University of Southampton, UK
A. Cavaleiro, University of Coimbra, Portugal
Correspondent: Click to Email
Binary TiN and ternary (TiX)N hard coatings, with X = Cr, Al, Si, Cr, etc, are well established in commercial tribological applications due to their high oxidation resistance and high hardness. Such coatings have been used to protect the surface of milling and machining tools; however, their friction coefficient revealed to be fairly high, at high temperature. This is a key point during machining of low thermal conductivity materials such as Ti-alloys. Liquid lubricants and oils have been used to reduce the friction and temperature between the sliding contacts; however, they frequently volatilize at high temperature, leading frequently to the failure of the cutting tools and, consequently, to increasing machine down times. To face these problems, solid lubricant coatings have been developed in the last decades to reduce the friction coefficient. The approach has been combining the intrinsic properties of binary and ternary coatings with elements that give lubricious properties, as it is the case of V. Such element forms thin reaction films of V-O on the surface of coatings with interesting properties at high temperature. Thus, the main goal of this work was to study the effect of V content on the oxidation and tribological properties of TiSi(V)N coatings deposited by DC reactive magnetron sputtering. Comparison of these results with those achieved for TiN, and TiSiN coatings prepared as references is also provided. The oxidation resistance of films was characterized by thermo gravimetric analysis and the tribological properties evaluated in pin-on-disc wear equipment, using as counterparts Al2O3 and HSS balls. V additions increased the oxidation rate and decreased the friction coefficient and volume loss of coatings. SEM and Raman analysis showed that V2O5 phase is the responsible for this tribological performance. TiSiN displayed the lowest wear resistance among all the tested coatings.