Plasma spray coated ceramic bodies and method of making same

A subentry shroud or nozzle for use in delivering molten metal below the surface of a molten slag layer in a continuous casting mold, comprising:

• an elongated body member of a compacted and fired fused silica material having an internal bore extending from a first end to a second end thereof for delivering a flow of molten metal from said first end to said second end below the surface of said bath of molten material, said body member also having an outer sidewall surface extending between said first and second ends, a portion of said outer surface adapted to contact the surface of said molten slag layer and defining a slagline area therearound;
• a plasma sprayed layer consisting essentially of zirconia coating said outer surface of the body in said slagline area, said plasma sprayed layer having an apparent porosity of at least 15% lower than an apparent porosity of said body, whereby said plasma sprayed layer is adapted to resist corrosive and erosive attack of the molten material at an attack rate lower than that of the body member;
• and
• at least one plasma sprayed intermediate layer containing some quantity of zirconium silicate positioned between said fused silica body and said corrosion and erosion resistant zirconia outer layer, whereby in use, said at least one intermediate layer is adapted to provide a transition in thermal expansion between the body member and the outer layer to minimize thermal induced cracking in said outer layer.