Two-step carbothermal reduction-carburization synthesis of high-quality (Ti, W)C solid solution powders for high-performance cermets

This study proposed a two-step carbothermal reduction-carburization method for preparing high-quality (Ti, W)C solid solution powders. Through separating the carbothermal reduction deoxygenation from the carburization and solid solution process, stepwise precise control was achieved. Using TiO 2 , WO 3 , and carbon black as raw materials, deoxygenation and most of the solid solution reactions were first completed at 1500 °C under a carbon-deficient condition. Subsequently, precise carbon supplementation was conducted, followed by final carburization and solid solution at 1550 °C. The resulting powders possessed excellent characteristics including elevated purity, fine grain size, homogeneous morphology, and optimal dispersibility. High-frequency spark plasma sintering (HF-SPS) was employed subsequently to fabricate (Ti, W)C-based cermets. A systematic elucidation of the reaction mechanisms in the two-step method was conducted, and the effects of W content on the powder characteristics as well as the microstructure and properties of cermets were explored. Results demonstrated that the grain size of the synthesized powders gradually decreased as W content increased, and (Ti 0.69 , W 0.31 )C showed the finest average grain size (0.38 ± 0.12 μm). Increasing W led to a decline in both hardness and fracture toughness ( K IC ) of cermets. Cermet sintered from (Ti 0.88 , W 0.12 )C powder demonstrated optimal mechanical properties, and possessed a hardness of 2030 ± 21 HV 30 and a K IC of 10.35 ± 0.31 MPa m 1/2 , achieving an excellent combination of hardness and toughness.