Influence of Ru, Mo and Ir on the Behavior of Ni-Based MCrAlY Coatings in High Temperature Oxidation

To improve the oxidation/corrosion resistance of MCrAlY coatings (M for Ni and/or Co), elements like Y, Si and Ta have been added into the coatings in past decades. In this study the oxidation performance of a Ni-based MCrAlY coating with small proportion of Ru, Mo and/or Ir were investigated after high-temperature exposure. The oxidation tests were carried out at 900°C, 1000°C or 1100°C. The micro structure study showed that the addition of Ru, Mo and/or Ir had significant influence on the oxidation behavior at the coating surface and the microstructural evolution in the material. The microstructural evolution was quantitatively evaluated by measuring the phase degradation of β-NiAl in the coating and γ′-Ni₃Al in the substrate of superalloy. Since no oxides of Ru, Mo and Ir were found on the coating surface, it was believed that the effects by those elements were mainly due to their dissolution in the metallic phases in the coatings.