The effect of post heat treatment and TiO2 addition on tribological and electrochemical performances of thermally sprayed alumina

Abstract

ABSTRACT The heat treatment of alumina ceramics is a fundamental process for controlling the physical, mechanical and thermal properties of these components during industrial operations. The problem statement in this case is about the effects of TiO2 addition and post heat-treatment on the expansion behaviour of alumina coating. For that alumina (Al-99) and alumina-titania coatings 5% wt. TiO2 (AT-5) and 15% wt. TiO2 (AT-15) were formed onto E335 substrate steel via the flame spraying technique. The samples were heat-treated (1000°C for 2 h in Air) and their wear and electrochemical behaviour was compared with the as-sprayed samples. The X-ray diffraction (XRD) patterns reveal a change in the phase composition of the heat-treated coatings compared to the as-sprayed coatings, as alpha alumina matrix but with different ratio. The heat-treated coatings exhibit higher values to as-sprayed coating. At the same time, the addition of TiO2 present hardness twice than pure alumina coating (Al-99). The tribological properties show that the deposits after heat treatment have low wear values compared to the as-sprayed coatings, the lowest specific wear rate was obtained for the heat-treated AT-5 composite coatings. The heat treatment had a positive effect on the corrosion resistance.