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 68wt% 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. © 2008 ISIJ.