The structure and high temperature corrosion performance of medium-thickness aluminide coatings on nickel-based superalloy GTD-111

Simple and Si-modified aluminide coatings having medium-thickness (40–60 μm) have been applied on the superalloy GTD-111 by a slurry technique. Hot corrosion and cyclic oxidation performance of the uncoated and the coated superalloy were investigated by exposing samples to a molten film of Na2SO4-40 %wt NaVO3-10%wt NaCl at 780 °C and 1 h cyclic oxidation at 1100 °C in air, respectively. The presence of silicon in the aluminide structure increased the oxidation resistance by a factor of 1.7 times. In addition, a SiO2-containing scale, which formed on the Si-containing coating surface, was stable during of the hot corrosion testing.

Research highlights
► The coating grows inwardly during slurry silicoaluminizing process.
► The presence of silicon in aluminide structure increased the oxidation resistance.
► No catastrophic failure observed for the Si–aluminide coating in the oxidation test.
► The Si–aluminide coating was stable during of the hot corrosion testing.