Influence of alloying elements on hot corrosion of superalloys and coatings: necessity of smart coatings for gas turbine engines

Modern gas turbine engines require high performance materials and coatings to ensure high efficiency. The selection of high performance materials and coatings depends on the nature and concentration of alloying elements. The composition of materials and coatings, in particular, plays a major role in enhancing the life of gas turbine engines by exhibiting good resistance to oxidation and hot corrosion, which are major problems in gas turbine engines. The performances of several superalloys containing different alloying elements and MCrAIY type coatings containing a variety of major and minor alloying elements are described in detail. The effect of major and trace elements on the life of superalloys and coatings in the presence of pure Na2SO4, NaCl and vanadium containing environments is detailed. The relevant reaction mechanisms leading to the failure of superalloys and coatings are discussed. The major factors involved when selecting alloying elements for the preparation of superalloys to manufacture components intended for use under hot corrosion conditions and the selection of appropriate coatings are suggested. Finally, the necessity of innovation of `smart coatings' to combat both oxidation and hot corrosion is discussed.