The Effect of Ti on the Early Stages of Oxidation of an Alumina-Forming NiCrAl Alloy

Abstract

Model γ-NiCrAl alloys with and without titanium were oxidized for short times up to 32\xa0h at 1000\xa0°C and subsequently characterized by scanning electron microscopy, transmission electron microscopy, and atom probe tomography in order to clarify the role of Ti on the oxidation behavior of alumina-forming nickel alloys. At the longer oxidation times, Ti was found to have no significant effect on the major protective oxide phases formed and overall scale and individual oxide layer thicknesses. Ti was observed to segregate to interfaces within the scale and form a Ti-rich oxide at the scale surface over time. At the shortest oxidation times before a continuous Al2O3 layer formed, the Ti-containing alloys exhibited thicker Cr2O3 layers, suggesting that Ti accelerates Cr2O3 growth kinetics. Additionally, oxide nodules resulting from fast oxidation of TiN particles were observed on the Ti-containing alloys. These may be linked to increased spalling propensity of Ti-containing alloys.Graphical Abstract