Revealing the elusive role of water vapor in the oxidation behavior of a Mn-Si containing NiCr alloy at 950 °C

Detailed nanoscale characterizations revealed the formation of a considerably higher fraction of SiO2 particles in the external Cr2O3 layer on a NiCr alloy. In addition, atom probe tomography revealed substantially lower segregation of Mn 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 regarding the impact of distinct transport processes through the Cr2O3 layer on the resulting oxidation rates and subsurface alloy compositional changes.