Effect of pre-oxidation and sea salt on the hot corrosion behavior of MCrAlY coatings and Al[sbnd]Si coatings

Abstract

This paper investigated the hot corrosion behavior of two types of coatings, namely NiCoCrAlYHfSi and AlSi coatings, used in gas turbines operating in a moderate-temperature sea salt environment. Prior to the corrosion experiment, pre-oxidation treatment was employed to generate a continuous α-Al2O3 thin layer on the surface of the coatings, leading to a significant reduction in coating roughness. The results demonstrated distinct failure behaviors of the two coatings in the presence of sea salt, providing insights into the mechanism of hot corrosion. The NiCoCrAlYHfSi coating effectively resisted corrosion through a mixed oxide layer consisting of Al2O3 and Cr2O3, while the AlSi coating utilized the continuous formation of Al2O3 to combat corrosion. In comparison to the NiCoCrAlYHfSi coating, the AlSi coating exhibited superior resistance to sea salt erosion. In addition, pre-oxidation is able to effectively reduce the erosion of the coating by sea salt, thereby extending the lifespan of the NiCoCrAlYHfSi coating and the AlSi coating by 40 % and 30 % respectively.