Oxidation and alkali sulphate-induced corrosion of aluminide diffusion coatings with and without platinum

Book chapter, 2023

Ni-based superalloys are extensively used as components in stationary gas turbines. The most frequently encountered form of such corrosion is alkali sulphate hot corrosion. Aluminide coatings are widely used to improve the oxidation resistance of Ni-base superalloy turbine components during high-temperature oxidation and/or corrosion. The environmental conditions of turbines have been simulated by salt deposition and subsequent tube-furnace laboratory experiments. Corrosion and oxidation exposures were performed on platinum-rich and platinum-free coatings. Traces of transient alumina were detected on platinum-rich samples during corrosion but were difficult to quantify. The aluminium oxide scale is thicker in the case of corrosion, which causes more spallation. In the platinum-rich coating, the depletion of the aluminium reservoir to 32% was first observed after 500 h of oxidation at 1050 °C. Corrosion and oxidation exposures were performed on platinum-rich and platinum-free coatings.