Unveiling the Selective Oxidation Mechanism of a Low Cr Alloy with Surface Spraying Oxide Nanoparticles of hcp Structure

Abstract

This study systematically explored the oxidation behavior of a Ni-10Cr alloy without and with surface spraying hexagonal closed pack (hcp)-structured α-Al₂O₃ or α-Fe₂O₃ nanoparticles. Despite the distinct equilibrium dissociation oxygen partial pressure of the two kinds of oxide nanoparticles, they both contributed to the selective oxidation of Ni-10Cr alloy, achieving the transition from internal Cr oxidation to external Cr₂O₃ scale formation. Nano-scaled characterization indicates that a coherent interface was developed between the newly grown Cr₂O₃ grains and the hcp-structured oxide nanoparticles, whereby promoting epitaxial Cr₂O₃ nucleation surrounding the nanoparticles and kinetically accelerating the formation of a continuous Cr₂O₃ scale at the transient oxidation stage. The findings provide new insights into the selective oxidation mechanism of alloys with low Cr contents.