Isothermal oxidation studies were conducted on Nicrofer-6025HT alloy in the temperature range of 700°C to 900°C up to 24 hours. Surface analysis using SEM revealed that the growth of chromia occurred along the grain and twin boundaries. The surface also contained reactive element oxides along the twin and grain boundaries. XRD analysis of the oxide scale indicated the presence of Al2O3, Cr2O3 and NiCr2O4. Cross sectional SEM analysis revealed a composite oxide scale formation on Nicrofer-6025HT, consisting of an outer rich chromia scale and an inner oxide scale of alumina. Traces of titanium and silicon were also identified in the oxide scale while NiCr2O4 spinel phase was located at the interface for the longer times at high temperatures evaluated. Establishment of compact layer of Cr2O3 resulted in a decrease in its own thickening rate but accelerated the formation of Al2O3 at the interface. XPS analysis revealed the presence of iron oxide and nickel oxide in minor quantities on the oxide surface.
Revised: May 11, 2016 |
Published: January 26, 2013