Fabrication process of spinel powder for plasma spraying

Spinel powders for plasma spraying were fabricated for application as prote ctive coatings against chemical attack from fused metal or glass. Due to th e complex structure of spinels, the process of fabrication of the powder ne eded several steps to get rounded, well-crystallized grains. This consisted of spray-drying, sintering in an electrical furnace and then melting in an induction plasma. Several compositions were made and powders were then pla sma sprayed on steels. Following the initial compostion, preferential volat ilization was observed due to the successive thermal treatments, leading to coatings having compositions different from the powder. The microstructure and homogeneity of the coatings was also studied using scanning electron m icroscopy. (C) 1998 Elsevier Science Limited. All rights reserved.