Characterization of glass-alumina functionally graded coatings obtained by plasma spraying

Glass-alumina functionally graded coatings (FGCs) were produced Via plasma spraying, a deposition technique for thick (> 10-20 mu m) coatings production, which ensures high flexibility and good reliability. The samples were obtained by building a graded glass-alumina coating onto an alumina substrate; the coatings were designed as multi-layered systems, each layer having a mean composition slightly different from the neighbouring ones. Two different compositional gradients were considered (front 100 vol.% alumina to 100 vol.% glass and from 80-20 vol.% glass to 100 vol.% glass) and several heat treatments were performed in order to improve the substrate-coating interface and induce a controlled transformation (sintering and/or crystallization) of the glassy phase. After a preliminary screening of the as-sprayed and the heat treated samples, the most interesting ones were carefully characterized, especially from a mechanical point of view. In fact, tests Such as Vickers micro-indentation allowed to appreciate the effects of the graded compositional profile and the consequences induced by thermal treatments. (c) 2006 Elsevier Ltd. All rights reserved.