In-situ synthesis of multiphase carbides/high-entropy alloy gradient composites by high-gravity combustion route

High-gravity combustion synthesis (HGCS) technique can simultaneously generate high-gravity and ultrahigh temperature fields, making it highly suitable for the efficient in-situ synthesis of ceramic/metal composite materials and offering significant potential for practical applications. In this study, multiphase carbides/high-entropy alloy (HEA) gradient composites were prepared by in-situ HGCS technique using multiphase thermite (Co₃O₄, Cr₂O₃, Fe₂O₃, NiO, and Al powders) and WC composite powders as raw materials. In this process, the highly exothermic thermite reaction formed the high-temperature HEA melt, which then reacted with WC to synthesize various carbides, including M₃W₃C (η phase, M = Co, Cr, Fe, Ni), W₂C, and Cr₂₃C₆. Under the influence of high-gravity field, various carbides move separately in the HEA melt due to their different densities, and eventually solidify rapidly into gradient composites. This structural configuration results in a gradient variation in mechanical properties along the high-gravity direction, with the Vickers hardness increasing from 419 HV1 to 893 HV1 and the average friction coefficient decreasing from 0.76 to 0.27. In addition, the calculation results of the phase separation kinetics between M₃W₃C particles, Al₂O₃ particles, bubbles, and HEA melt show that larger high-gravity coefficients, larger particle sizes, and longer retention time of the HEA melt lead to larger motion displacements of the dispersed phases. To evaluate the application potential of the gradient composites, the material was prepared into agricultural cutting blades for agricultural harvesting tests. The results showed that the gradient composites cutting blades exhibit excellent self-sharpening performance.