A novel method to promote selective oxidation of Ni-Cr alloys: Surface spreading α-Al2O3 nanoparticles

Following Wagner's classical oxidation theory, we suppose that a Ni-Cr alloy with the Cr concentration below the critical N-Cr((1)) (0.24) required for external Cr2O3 scale formation but above the critical N-Cr((2)) (0.1) required for its steady-state growth, would be converted from a NiO former to a Cr2O3 former, if the selective Cr oxidation of the binary alloy can be catalyzed at the beginning of oxidation. As is expected, spreading alpha-Al2O3 nanoparticles on the surface of Ni-10Cr (N-Cr = 0.11) does cause it to become a Cr2O3 former during oxidation at 800 degrees C. The alpha-Al2O3 effect on oxidation is interpreted.

Automated summary

According to Wagner's classical oxidation theory, a Ni-Cr alloy with Cr concentration below the critical level for external Cr2O3 scale formation but above the level for steady-state growth, can be converted from a NiO former to a Cr2O3 former by catalyzing selective Cr oxidation at the beginning of oxidation. When alpha-Al2O3 nanoparticles are spread on the surface, it causes the Ni-10Cr alloy to become a Cr2O3 former during oxidation at 800 degrees C. The effect of alpha-Al2O3 on oxidation is explained.