Oxidation behavior of TiC-containing Ti₃AlC₂ based material at 500–900 °C in air

Abstract

The isothermal oxidation behavior of Ti₃AlC₂ based material containing 5 vol% TiC inclusion in air had been investigated at 500–900 °C by means of TGA, XRD, Raman spectroscopy and SEM/EDS. It was demonstrated that, although Ti₃AlC₂ based material exhibited good oxidation resistance at temperatures above 700 °C, anomalous oxidation with higher oxidation rate occurred at lower temperatures of 500 and 600 °C. This interesting phenomenon was due to the formation of microcracks associated with the stress developed within the scales, mainly consisting of anatase, and the volume expansion as Ti₃AlC₂ based material was directly exposed to air at those temperatures. Its oxidation, at temperatures investigated with the exception of 600 °C, generally obeyed a parabolic rate law. The weight gain data for the remaining temperatures were analyzed with an instantaneous parabolic rate constant method by assuming a parabolic rate law. The variations of instantaneous parabolic rate constant with time reflected the complexity of the oxidation behavior of Ti₃AlC₂ based material. These variations were discussed from the viewpoint of the formation of microcracks at 500 °C, and preferred oxidation of TiC inclusion in the initial oxidation and its subsequent depletion at 800 and 900 °C on the basis of X-ray diffraction, Raman spectroscopy, SEM scale morphology observation and composition analysis using EDS. In addition, the deleterious effect of TiC inclusion on the oxidation resistance of Ti₃AlC₂ based material was also investigated and discussed with comparison to monolithic Ti₃AlC₂, which was helpful to understand the discrepancies in reports on the oxidation of Ti₃AlC₂.