PNNL

Abstract

Detailed nanoscale characterizations revealed the formation of a considerably higher fraction of SiO2 particles in the external Cr2O3 layer on a NiCr alloy while a substantially lower segregation of Mn was measured at the Cr2O3 grain boundaries in wet air compared to dry air exposures where the intriguing formation of Mn-rich clusters was observed in the Cr2O3 grains for the very first time. These findings provided additional evidence to the mechanisms proposed in an earlier work by the authors regarding the impact of distinct transport processes through the Cr2O3 layer on the resulting oxidation rates and subsurface alloy compositional changes.