Adding Cr and Mo simultaneously enhances the strength and impact toughness of TiC microparticle-reinforced steel matrix composites at high temperatures

Abstract

The excellent mechanical properties of titanium carbide (TiC) microparticle-reinforced steel matrix composites make them particularly applicable in engineering. In this study, the influence of adding Cr and Mo on the strength and impact toughness of TiC microparticle-reinforced steel matrix composites at 25–600 °C was systematically analysed and the strengthening and toughness mechanisms were elucidated. The results showed that the strength and impact toughness of the TiC microparticle-reinforced steel matrix composites at high temperatures were simultaneously enhanced by adding 3 wt% Cr and 0.5 wt% Mo. Cr and Mo mainly increased the contributions of dislocation, precipitation and solution strengthening by reducing the dislocation annihilation and the coarsening rate of carbides. Moreover, improving the tempering stability of the matrix increased the failure temperature of the TiC microparticles from 500°C to 600°C by adding Cr and Mo. The volume fraction of V1/V2 variant pairs with a 60° misorientation angle was increased by increasing the driving force of the phase transformation. Combined with the recovery of martensite at high temperatures, the density of the high-angle grain boundaries was increased, resulting in greater impact toughness at high temperatures.