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

Abstract 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 α-Al2O3 nanoparticles on the surface of Ni-10Cr (NCr = 0.11) does cause it to become a Cr2O3 former during oxidation at 800 °C. The α-Al2O3 effect on oxidation is interpreted.