High temperature corrosion is a grave problem in incinerators, boilers, turbines and IC engines. To prevent hot corrosion, alloying of metals is usually done. But it does not conserve mechanical properties like creep, toughness, ductility etc. Coating is a generic way to enhance the materials life at elevated temperature in the presence of salts. Sol-gel method of coating is easy and cheap as compared to thermal spray coatings. In the present work, Cerium substituted Silicon-Zirconium coating is prepared via Sol-Gel route. It is deposited on Chromium based super alloy SS-304. Sol-gel dip coating method is used for coating the materials. Cyclic oxidation tests are performed at 900°C in the presence of Na2SO4 salt solution on coated and bare samples. The weight gain analysis shows that coated samples have shown better corrosion resistance than bare specimen cyclic oxidation in simulated environment. SEM, EDS and X-ray mapping techniques are also confirmed that organic precursors of Silicon and Zirconium useful in creating uniform coating. However, coating showed cracks after calcinations which may be due to higher rate of drying. But cracks become self-healed when specimen was subjected to simulated environment at 900°C due to grain growth of Zirconium particles. X-ray mapping showed that protective layer of cerium and Zirconium present at surface of SS-304 and coating was successful in providing resistance to substrate metal from penetration of salts.
Hot corrosion behaviour of plasma and d-gun sprayed coatings on t91 steel used in boiler applications