MICROSTRUCTURAL STUDY OF THE HOT CORROSION OF A CALCIUM ALUMINOSILICATE GLASS-CERAMIC AND A SI-C-O-FIBER-REINFORCED CALCIUM ALUMINOSILICATEMATRIX COMPOSITE VIA SODIUM-SULFATE IN AIR AND ARGON AT 900-DEGREES-C

The hot corrosion of a calcium aluminosilicate (GAS) glass-ceramic and a composite of CAS matrix that has been reinforced with Si-C-O (Nical on) fiber has been investigated by X-ray diffractometry, scanning elec tron microscopy, and transmission electron microscopy. Samples of the monolithic CAS and the Si-C-O-CAS composite were subjected to corrosio n using liquid sodium sulfate at 900 degrees C for 50 h in air and arg on environments, The monolithic and composite samples both were corrod ed by sodium sulfate, and corrosion damage in the composites was more severe than in the monolithic GAS, irrespective of the gaseous environ ment, The increased corrosion damage in the composites was due to the presence of Si-C-O fibers, which changes the mechanism of corrosion. T he corrosion products in monolithic CAS were different from those in t he composites; this disparity was also due to the presence of the fibe rs in the composite, The corrosion zones in all the samples were sever ely cracked, and the cracks extended into the unaffected regions of th e samples, Mechanisms of hot corrosion have been proposed and discusse d for both the monolithic and composite samples.