Fabrication of Steel Matrix Composite Locally Reinforced with in Situ TiC Particulate via SHS Reaction of (Ti, Fe)–C System during Casting

Abstract

The low-alloy steel matrix composites locally reinforced with in situ TiC particulates have been successfully produced utilizing the self-propagating high-temperature synthesis (SHS) reaction of (Ti, Fe)–C systems during casting. Two types of TiC particulates synthesized by different mechanisms exhibit a relatively uniform distribution in the local reinforcing region. The large rectangular TiC particulates with an average size of ~2 μm or more, which are formed by the nucleation-growth mechanism through the contact reaction process, are mainly present in the local reinforcing region of the composites fabricated by (28Ti, Fe)–C system and the matrix region nearby the interface between the steel matrix and reinforcing region. The fine spherical/near-spherical TiC particulates, which are synthesized by reaction, solution and precipitation mechanism during the SHS reaction, are mainly existent in the reinforcing region. Moreover, the average size of spherical/near-spherical TiC particulates increases from ~0.1 to ~0.5, and then to ~1 μm with the increase in Ti content from 28 to 48, and then to 68 wt% in (Ti, Fe) powders. The interfaces of the composites are clean, which results in a good metallurgical bonding between steel matrix and reinforcing region in the composites. Moreover, the micro-hardness and wear resistance of the local reinforcing region of the composites are significantly higher than those of the unreinforced steel matrix.