Effect of surface treatment and crystal orientation on hot corrosion of a Ni-based single-crystal superalloy

•Surface preparation affected the γ-γ’ volume partition and provoked deformations in some cases.•Type I hot corrosion showed stronger orientation and surface pre-treatment dependence than Type II.•Corrosion kinetics decreased in the sequence grit blast > electropolish > ground•{011} planes have shown higher protection against hot corrosion.•The importance of interdiffusion was confirmed in Type I. The effect of surface preparation and crystal orientation was investigated for a TMS-138 single crystal superalloy under Type I and Type II hot corrosion conditions. The superalloy was cut along the {100} and {110} planes on which grit blasting, mechanical polishing and electro-polishing surface finishes were conducted. At 900 °C grit blasting or electropolishing distorted the surface and altered the γ-γ’ structure of the alloy provoking higher corrosion rates than on mechanically polished surfaces. The electropolished surface revealed that crystal planes with higher atomic number density have an increased corrosion resistance. The anisotropy effects were not observed with Type II exposures.