Herbert Gasthuber

Tribological properties of thermal-sprayed Magnéli-type coatings with different stoichiometries (TinO2n−1)

Abstract This paper summarizes results on the possibility of coating aluminium with titania-based Magneli-type coatings by thermal spraying, as well as the tribological properties of these coatings. For this purpose, a spray powder with a defined phase composition was applied on AlMg substrates by atmospheric plasma spraying. Crystalline Magneli phases of the type Ti n O 2 n −1 with a crystallographic shear structure could be identified after spraying in the coating by means of X-ray diffraction. Dry sliding experiments were conducted on a high-temperature pin-on-disc test rig against polycrystalline alumina at 23 and 400°C up to a sliding distance of 2000 m at 1 m/s. The coefficient of friction (COF) remains high, at between 0.7 and 0.8 for all tests. The best wear results are achieved for the Ti 6 O 11 coatings, showing wear rates down to 1.2×10 −6 mm 3 /N m. The tribological behaviour of the sprayed coatings indicates strong anti-wear properties under dry sliding conditions. Under mixed/boundary-lubricated conditions, the interaction of a low-additive polyalkyleneglycol (PAG100) with Magneli-type phases results in very low friction and wear coefficients in the range of 10 −10 mm 3 /N m.