Influence of Rare Earth Y on Microstructure and High Temperature Oxidation Behavior of Ni-Fe-Co-Cu Alloy

The influence of rare earth Y on the microstructure and high-temperature oxidation performance of 45Ni-40Fe-8Co-7Cu alloy was studied. The results showed that the oxidation of 45Ni-40Fe-8Co-7Cu alloy at 850℃, under 0.101 MPa oxygen partial pressure followed the parabolic law and the oxidation rate constant was 1.83×10-10 g2•cm-4•s-1. The oxide film mainly consisted of the mixture of Fe2O3 and (Ni/Co)Fe2O4. After adding rare earth Y into the alloy, Ni-Y phase precipitates along the grain boundary. The higher the content of Y was, the more rare earth phases in the grain boundary. The high temperature oxidation of 45Ni-40Fe-8Co-7Cu-xY alloy still followed the parabolic law at 850℃. Moreover, the external diffusion of Ni was promoted due to the addition of Y. The oxide film mainly consisted of (NiCo)Fe2O4 spinel oxide. The oxide crystal particles of 45Ni-40Fe-8Co-7Cu alloy with 0.3% Y addition were fine and the film layer was compact and complete. Meanwhile, the parabolic oxidation rate constant of the alloy decreased to 1.15×10-10 g2•cm-4•s-1. Indicating that the addition of a small amount of (0.3%) rare earth Y refined the oxide crystal particles and improved the oxidation resistance of the alloy. With more addition of rare earth Y, not only the external diffusion of Ni was promoted, but also the internal diffusion of O speeded up during high temperature oxidation process. This would accelerate the oxidation of this alloy. © Editorial Office of Chinese Journal of Rare Metals. All right reserved.