SHS METALLURGY OF Cr2AlC MAX PHASE BASED CAST MATERIALS

The paper reviews literature on the structure, properties, production processes, and fields of application of materials based on the MAX phase Cr₂AlC. It was noted that the most promising method for production of such materials was self-propagating high-temperature synthesis (SHS), with SHS metallurgy being one of its directions. A mixture of AR grade chromium III and chromium VI oxide powders, ASD-1 grade aluminum, and carbon was used as the base charge during studies. The adiabatic combustion temperature and the composition of final products were calculated using the special THERMO program. The experiments were carried out in the SHS reactor with a volume of V = 3 dm³ at the initial inert gas pressure (Ar) Р₀ = 5 MPa. The experiments focused on the influence of the starting reagent ratio on parameters of the high-temperature synthesis (burning rate, pressure gain, and yield of the target product), composition and microstructure of target products. The paper develops a scientific approach to the production of cast materials by SHS metallurgy under gas pressure in the Cr–Al–C system consisting of the Cr₂AlC MAX phase, and Cr₅Al₈ and Cr₃C₂ phases. The paper studies structural-phase states of target products. It was experimentally established that by varying the content of starting reagents (aluminum and carbon) in the charge, it was possible to produce a significant effect on synthesis regularities, the composition and microstructure of final products. As the carbon content in the base mixture increases (above the stoichiometric content), the content of the MAX phase Cr₂AlC in the final product increases as well and content of Cr₅Al₈ reduces. An increase in the aluminum content (above stoichiometric) in the base mixture leads to an increase in the MAX phase Cr₂AlC content in the final product and to a reduction in the Cr₃C₂ phase content. 

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