Thermal and chemical stability of Cr2AlC in contact with α-Al2O3and NiAl

Abstract

AbstractThe thermal and chemical stability of Cr2AlC, Cr2AlC–NiAl and Cr2AlC–α-Al2O3have been studied. No enthalpic effects indicating phase transformations or chemical reactions were observed for the Cr2AlC–α-Al2O3powder mixtures at T < 1476°C, while a melting onset temperature of 1310°C was measured for the Cr2AlC–NiAl powder mixture by differential thermal analysis. However, the formation of chromium carbide is also predicted to occur below this temperature based on our thermodynamic calculations, and was observed by X-ray diffraction of powders annealed at 1000 and 1300°C. The carbide formation is caused by the reaction of Cr2AlC with NiAl and can be understood by considering the large solid solution range of Al in NiAl. These results indicate that the application potential of Cr2AlC–NiAl composites is limited by the Al solubility in the NiAl.