Cast Mo–Cr, W–Cr, and Cr–Al Master Alloys by Gravity-Assisted SHS Metallurgy

Abstract

Cast Mo–Cr, W–Cr, and Cr–Al master alloys were prepared via centrifugal SHS metallurgy. The effect of variation in component fractions in green mixtures (100 – α)(Cr₂O₃ + Al) + α(MoO₃ + Al) and (100 – α)(Cr₂O₃ + Al) + α(WO₃ + Al) on the synthesis of Mo–Cr and W–Cr alloys, respectively, was thermodynamically analyzed. Thermodynamic calculation of Cr–Al master alloy production was presented and provided the necessity of using a complex oxidizing agent, chromium(III) oxide and chromium(VI) oxide in a certain ratio. Experiments for Mo–Cr, W–Cr, and Cr–Al systems proved the necessity of applying overloading at an acceleration of no less than 50 g to prolong the lifetime of the melt. Introduction of functional additives CaF₂ (fluorspar) and sodium hexafluoroaluminate Na₃[AlF₆] (cryolite) to the green mixture lowered the melting temperature of the slag phase (reduced its viscosity) and facilitated the phase separation. EDS and mass spectroscopy analyses showed that the chemical compositions of synthesized master alloys are close to their calculated and target values. XRD results revealed the existence of solid solutions based on target elements.