Gas Phase Initial Oxidation of Incoloy 800 Surfaces

Abstract

The surface oxidation of Incoloy 800 was studied using dilute O2 gas at temperatures of 300 °C. Samples with two differing grain sizes were studied using time-of flight secondary ion mass spectrometry (ToF–SIMS) and X-ray photoelectron spectroscopy (XPS) as primary analysis tools. A multi-layered oxide film was detected and was composed of an exterior gamma-Fe2O3 with a Cr2O3 layer at the oxide–metal interface also containing significant concentrations of NiCr2O4. Minor concentrations of another spinel oxide, NiFe2O4 were distributed throughout the film. The kinetics of oxidation growth was found to follow a direct logarithmic relationship for both grain sizes, suggesting that the oxide would be a suitably protective. Very small oxide nodules formed at later stages, particularly for the small grained samples. A protocol for assessment of XPS spectral envelopes is advanced. The method measures the percent residual intensities remaining after spectral subtraction of reference spectra and appears to be an effective means for screening of possible components.