Diverse scaling behavior of the Ni–20Cr alloy

A study was undertaken to investigate the isothermal oxidation behavior of the Ni–20Cr binary alloy at 750 and 1000 °C. The samples were exposed in air for 6 and 50 h. The oxide phases formed on the alloy were α-Cr2O3, NiCr2O4 and NiO. Microstructural examination of the alloy perpendicular to the plane of oxidation revealed co-lateral formation of diverse scale configuration at its surface. The thickness of the scale formed on the alloy surface varied from 1.5 to 18 μm. The protection imparted was due mainly to α-Cr2O3; however, various regions of the alloy surface constituted predominantly of NiCr2O4.