STUDIES ON CORROSION BEHAVIOUR OF STELLITE COATED MATERIALS AT HIGH TEMPERATURES

Abstract

The present study has been done on high temperature Fe-based alloy (X22CrMoV121) uncoated and coated with stellite. The study has been done in salt mixture. containing 5% NaCl and 95% Na2SO4 and in H2S environment. The erosion study has also been done on the same alloy with and without stellite coating. It has been found that stellite coating specimen shows more resistance to the salt environment with increase in temperature whereas base alloy nearly fails at higher temperature i.e. 900°C. The corroded specimens were studied by SEM, XRD and EPMA. The prominent phases present in case of specimen with-out stellite coating were Na2SO4 and FeS2 while in case of. specimen with stellite coating Fe203 has been mainly identified. In HS environment the performance of stellite coated specimen is inferior to the specimen without stellite coating. At 0 800C and 9000C the stellite coated specimen shows larger weight loss as compared to specimen without stellite coating. The corroded specimens were studied by SEM, XRD and EPMA. The erosion study shows that although initial weight loss is more in stellite coated specimen as compared to specimen without stellite coating, the weight loss decreases in stellite coated specimen with increase in exposure time. Pits are observed in specimen without stellite coating whereas the specimen with stellite coating showed mirror finish without indication of pitting.