A comparative study on the oxidation behavior of Y-, Hf- and YHf-doped NiCoCrAl alloys: Effect of reactive elements

Abstract

This study investigates the effect of Y, Hf and Y/Hf addition on oxidation behavior of NiCoCrAl alloys at 1100 °C. It is demonstrated that Hf is most effective in reducing the oxide growth rate, while co-doping Y and Hf doesn’t result in a synergistic effect in slowing down oxidation rate. Formation of interfacial voids is inhibited in NiCoCrAlY and NiCoCrAlYHf, suggesting that Y is more effective in improving the resistance to oxide spallation. A new model based on the ionic radii of reactive elements (REs) and bonding strength of RE-O is proposed to guide alloy design for improved oxidation resistance.