Effects of B content and wear parameters on dry sliding wear behaviors of nanocomposite Ti–B–N thin films

Abstract

Ti–B–N thin films of ∼1.4 μm in thickness with different B contents were deposited on Si(1 0 0) at room temperature by reactive unbalanced dc-magnetron sputtering. Dry sliding wear behaviors of Ti–B–N films were investigated by a traditional pin-on-disk test. The worn surface was observed using optical microscopy, scanning electron microscopy (SEM), and the wear debris was analyzed by energy dispersion X-ray spectroscopy (EDX), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The results indicated that both boron content and wear test parameters had a great effect on friction coefficient and wear rate, as well as the corresponding wear mechanism. With incorporation of boron into TiN or increasing boron content, both friction coefficient and specific wear rate were decreased, accompanying with a change in wear mode from abrasive wear to dominant adhesive one. An inverse trend occurred in the wear rate when B content reached a critical value (∼42 at.% in the present study), which was due to the formation of hexagonal BN phase. With increasing applied loading from 2 to 10 N, the friction coefficient was increased, however the specific wear rate was decreased, accompanying with an increase of the amount of deformed wear debris. Increasing sliding velocity yielded similar results to increasing load, which was due to the strain rate effect. H 2O in air reacted with films during sliding tests, and hence produced Ti oxides of various types, TiO, TiO 2 and Ti 2O 3, together with a minor amount of FeO in debris, which was believed to improve wear resistance.