The importance of grain boundaries on the reactive elements effect in β-NiAlHf alloy

Cyclic oxidation of single crystalline and polycrystalline β-NiAlHf alloy was investigated at 1200 °C. The effect of grain boundary on the role of reactive elements was discussed. The results indicate that Hf effectively reduced the oxide scale growth rate and enhanced the scale adhesion in polycrystalline NiAl. But the single crystalline NiAlHf exhibits a higher oxide scale growth rate, severer internal oxidation and catastrophic scale spallation. The absence of the grain boundary leads to the negative effects of Hf.