On the Role of Yttrium in Alumina Formers: Comparative Oxidation Behavior of (Ni-Cr-Al)- and (Ni-Cr-Al-Y)-Based Alloys

摘要

It is shown that the addition of Y to an alloy based upon the Ni-Cr-Al system slightly reduces the growth rate of Al2O3 scale during isothermal oxidation in air at temperatures in the range of 950-1150 A degrees C. However, Y segregation at grain boundaries of the oxide is found to refine its grain structure down to the nanoscale with improved mechanical strength as compared to the Y-free alloy. It is concluded that Y can have the effect of decelerating the kinetics of diffusion processes leading to grain growth of the oxide.