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Ultrafine Ti(C, N)-based cermets are vacuum-sintered by refining the particle size of raw materials and tailoring the WC/TaC ratio to achieve the improvements in comprehensive mechanical properties and cutting performance. The hardness, flexural strength and tool lifespan of ultrafine Ti(C, N)-based cermets are substantially higher than those of submicron Ti(C, N)-based cermets with the same composition because of the refined grains and the improved distributions of both metal phases and residual stress. The hardness attenuation behavior and strengthening mechanism in Ti(C, N)-based cermets at different test temperatures have been proposed. At 400 ℃, the hardness attenuation of Ti(C, N)-based cermets depends mainly upon the softening of metal phases. However, at 800 ℃, the hardness attenuation of Ti(C, N)-based cermets is mainly related to the reduced bearing capacity of hard ceramic phases and interfacial sliding. The addition of refractory TaC is beneficial for the improvement of high-temperature mechanical properties and the tool lifespan, attributed to the strengthening of the ceramic framework by tantalum atoms. • The strategy on synergistic refinement of raw powders with various constituents in ultrafine Ti(C, N)-based cermets is proposed for the first time. • The comprehensive properties of ultrafine Ti(C, N)-based cermets are substantially higher than those of submicron Ti(C, N)-based cermets. • The hardness attenuation behavior and strengthening mechanism in Ti(C, N)-based cermets at different test temperatures are proposed. [ABSTRACT FROM AUTHOR]