High-Temperature Synthesis of Cast Materials Based on the MAX Phase Cr₂AlC Using CaCrO₄ + Al + C Mixtures

Abstract—

Experimental data are presented on the high-temperature synthesis of cast composite materials in the Cr–Al–C system with different relative amounts of the MAX phase Cr₂AlC and chromium carbides and aluminides. The experiments were carried out in multipurpose self-propagating high-temperature synthesis (SHS) reactors at an argon pressure p = 5 MPa. The starting mixtures consisted of calcium chromate (CaCrO₄), aluminum (ASD-1), and carbon powders. It has been shown that varying the percentage of carbon in the starting mixture may have a significant effect on the synthesis process and the phase composition and microstructure of the final products. It has been found that, in the case of the stoichiometric starting mixture composition, the synthesis yields cast composite materials consisting predominantly of the MAX phase Cr₂AlC and containing the lower chromium carbide Cr₇C₃ and the chromium aluminide Cr₅Al₈. The addition of excess (superstoichiometric) carbon to the starting mixture leads to an increase in the percentage of the MAX phase Cr₂AlC in the synthesis product, disappearance of the chromium aluminide Cr₅Al₈, and the formation of the higher chromium carbide Cr₃C₂ instead of the lower carbide. The final synthesis products have been characterized by X-ray diffraction and local microstructural analysis. The structure and composition of the synthesis products obtained under various conditions have been determined.