Influence of vacuum heat treatment parameters on the surface composition of MCrAlY coatings

► Vacuum heat treatment of MCrAlY coatings with various Y and O contents studied. ► MCrAlY coating surface composition is governed by competing Cr evaporation and Y oxidation. ► Cr is likely to evaporate as metallic species. ► Cr-evaporation is enhanced by reducing vacuum pressure and lowering Y content. ► Alumina formation is suppressed by both Y-oxidation and Cr-evaporation.