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

Abstract

The thermal and chemical stability of Cr2AlC, Cr2AlC–NiAl and Cr2AlC–α-Al2O3 have been studied. No enthalpic effects indicating phase transformations or chemical reactions were observed for the Cr2AlC–α-Al2O3 powder 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.

Interfacial reactions of a MAX phase/superalloy hybrid

“…Also, it has been predicted thermodynamically and shown experimentally that NiAl will deplete Al from Cr 2 AlC to form Cr 7 C 3. Given that Al in Cr 2 AlC interdiffused with the nickel superalloy, Cr 7 C 3 is an expected depletion zone in this LSHR–Cr 2 AlC couple. Finally, some W, Mo, Ni, and Co have been observed in the Cr 7 C 3 phase at the innermost region of the reaction layer, showing the limited extent of diffusion of these elements from the superalloy.…”