High Temperature Corrosion Resistance of Pt-Based Superalloys in 0.2% SO2-N2 Gas

Pt-based superalloys are a new generation of materials intended to be used in various high temperatureapplications. Effluent gases emitted to the environment during combustion operations can lead to degradation of hightemperature materials with deleterious effects on mechanical integrity and the corrosion of alloys. This paper focuses onsulphidation of one quaternary, and four ternary, Pt-based superalloys of various chemical compositions. Pt-basedsuperalloys were exposed at 900 ° C in a reducing environment. The alloys were compared to coated and uncoatedNi-based superalloys (NBSAs). X-Ray diffraction (XRD), Scanning electron microscopy (SEM) and Raman spectroscopywere used to characterize corrosion products that formed. The Pt-based superalloys exhibited higher corrosion resistancethan NBSAs as a result of the formation of a protective Al 2 O 3 scale, whereas NBSAs suffered internal sulphidation andformed Cr and Ni sulphide corrosion compounds. The formation of brittle needle-like phases and the transformation of theNiAl phase to Ni 3 Al, led to early failure of the coated alloy. Pt-based superalloys alloyed with Co showed poor corrosionresistance as a result of depletion of alloying elements.