Microstructure evolution of Cr2AlC MAX phase under a graphite bed between 1100 °C and 1500 °C

摘要

? 2022Thermal decomposition behaviors and microstructure evolution of porous Cr2AlC pellet samples in a graphite bed (65 N2 and 35 CO) between 1100 °C and 1500 °C were investigated to explore its potential slag-contact application. A walnut-like structure made of a porous chromium carbides core and Al2O3 shell was confirmed on the original Cr2AlC particle because of the formation of Al-depleted Cr2Al1-xC in the graphite bed atmosphere. After heat treatment at 1300 °C, depletion of Al within the Cr2AlC particle caused to generate a ～650 μm thickness CrCx-enriched layer on the sample's surface and a highest Vickers hardness of 13.7 GPa. When the temperature rose to 1500 °C, cracks occurred in the sample because of the volumetric expansion from further decomposition. The degradation mechanism of fine-Cr2AlC particles in the range from 1100 °C to 1500 °C was proposed in detail.