Plasma spraying of a novel material with amorphous and nanocrystalline microstructure

A novel material has been used for plasma spraying by WSP\uae. The material is composed of three main phases, namely corundum (aluminum oxide), baddeleyite (zirconium oxide), and glassy phase (silicon oxide). The material is a refractory and exhibits very high hardness, extremely high abrasion resistance, and chemical resistance. Conventionally, the material is fabricated by melt casting and machining. Cast tiles of the material were ground and sieved to obtain the right powder cut size for plasma spraying by water stabilized plasma torch (WSP\uae). Both dense coatings and free standing parts were successfully produced from the new material by WSP\uae. Spraying parameters were varied and molten particles were monitored in flight by DPV 2000. The coatings exhibit very low porosity and high hardness. The as-sprayed material is mostly amorphous with some nanocrystalline grains of aluminum and zirconium oxide present. The phase composition of the as-sprayed material is thus different from that of the feedstock material, which is mostly crystalline with a small faction of amorphous silica glass. The micro-structure of the newly sprayed material was studied by electron microscopy (SEM, TEM) and is very complex. Upon annealing, the as-sprayed material crystallizes around 950\ub0C. This result and other thermal properties were obtained by TMA and DTA measurement. The ease of plasma spraying and the coating properties make this material a suitable candidate for many industrial applications.Peer reviewed: NoNRC publication: Ye