Abstract
In this study, a hot corrosion scenario relevant to biomass-derived fuel-fired advanced land-based gas turbines is considered. The testing procedures take account of the different corrosive species (low sulfur, potassium-rich salts) and transient salt deposition conditions expected. These differ from those typically used to simulate Type I hot corrosion. A simplified cyclic hot corrosion test was applied, subjecting (K,Na)SO 4 -coated, cast nickel-base alloys, nickel alumides and a model electron beam physical vapor deposition (EB-PVD) thermal barrier coating (TBC) system to 1-h cycles at 950°C in flowing oxygen. Contaminant flux rate, salt recoating frequency and deposit removal/retention are important parameters to be controlled during testing. Cr rather than Pt and other precious metals such as Ir, Pd and Ru improves hot corrosion resistance of cast nickel aluminides. Practical implications for TBC systems are that molten deposits will be expected to primarily affect the bond coat by hot corrosion attack rather than degrade the ceramic top coating, thus indicating that both oxidation- and hot corrosion-resistant bond coats are needed to enable safe TBC operation.
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