SHS Metallurgy of Cr2AlC MAX Phase-Based Cast Materials

Аннотация

A review of publications on the structure, properties, fabrication methods, and application fields of materials based on the Cr₂AlC MAX phase is given. It is noted that the most promising method of formation of such materials is self-propagating high-temperature synthesis (SHS), one of the directions of which is SHS metallurgy. A powder mixture of chromium III and chromium VI oxides of the analytical grade, aluminum of ASD-1 grade, and carbon is used as the base charge in investigations. The adiabatic combustion temperature and composition of final products is calculated using the THERMO special program. Experiments were performed in an SHS reactor with volume V = 3 dm³ under the initial pressure of inert gas (Ar) P₀ = 5 MPa. The influence of the ratio of initial reagents on SHS parameters (the combustion rate, pressure increment, and yield of the target product), composition, and microstructure of target products is investigated experimentally. A scientific approach of the formation of cast materials in the Cr–Al–C system consisting of the Cr₂AlC MAX phase and phases Cr₃C₂ and Cr₅Al₈ by the SHS metallurgy method is developed. The structural-phase states of target products are studied. It is established experimentally that, varying the content of initial reagents (aluminum and carbon) in the charge, it is possible to substantially affect the synthesis regularities, composition, and microstructure of final products. An increase in the content of the Cr₂AlC MAX phase in the final product and a decrease in the Cr₅Al₈ content occur with an increase in the carbon content (above stoichiometric) in the initial mixture. An increase in the aluminum content (above stoichiometric) in the initial mixture leads to an increase in the content of the Cr₂AlC MAX phase in the final product and a decrease in the content of the Cr₃C₂ phase.