Tribological properties of silver- and copper-doped transition metal oxide coatings

Thin films of pure molybdenum oxide MoO3, vanadium oxide V2O5 as well as phases originating from Ag2O–MoO3, Cu–V2O5 and Ag–V2O5 systems were deposited on alumina substrates by means of reactive magnetron sputtering. Structure and phase composition of deposits were characterised by X-ray diffraction (XRD) and Raman spectroscopy. High temperature (100–700 °C) friction tests were performed using ball-on-disc configuration in air of normal humidity. Among studied phases, the best results were observed for silver molybdate (Ag2MoO4) and vanadium oxide bronze (β-Ag0,33V2O5) coatings, which were chemically stable and allowed to decrease friction coefficient to the level of 0.2 at 450 and 600 °C, respectively.