It is possible to enhance the high tempera-ture oxidation resistance and thus prolong the life time of non-oxide refractories by the application of oxide coating. In this -work, silicon nitride bonded silicon carbide refractories were coated with alumina using the plasma spraying technique. X-ray diffraction shouted r-Al2O3 to be the dominent phase in the as-sprayed alumina coatings. The stresses developed in the coating layer during post-spray heat-treatment have been analysed. It was found that the coating-was under a compressive stress below,but when heated above 1100C , the r-Al2O3 phase transformed into a-Al2O3 and this led to the formation of a destructive tensile stress(up to 1700 MPa) which caused cracks to form in and along the iveak bond between the alumina coating and SiC grains. The coatings then delaminated and of fered little protection to the refractory substrate from oxidation. Future research will be directed on the avoidance oj metastable phase formation in the plasma sprayed coating
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