The powder metallurgical incorporation of hard phases in steel matrices is an established concept to form a metal matrix composite with excellent mechanical properties. Especially TiC has been extensively used in a wide variety of steel matrices in the past. This is primarily due to its high hardness and decent bonding behavior towards steel matrices. While the stability of TiC particles is known to be low when powder consolidation involves a liquid phase, the thermodynamic stability during solid-state consolidation is less investigated. Moreover, the influence of particle size on the thermodynamic stability has not been examined in detail until now. Since the reaction of TiC with steel influences the chemical composition, and hence properties of the steel matrix, and reaction phases might affect its bonding behavior, which is assigned to be one crucial property for the abrasive performance of MMCs, it is of great importance to understand the parameters governing this behavior. To this end, this work investigates the thermodynamic stability and thus reaction phase formation as a function of the normalized surface area of TiC particles within a heat treatable steel consolidated by hot isostatic pressing. The evolved microstructures are investigated by scanning electron- and scanning transmission electron microcopy coupled with energy dispersive x-ray spectroscopy as well as x-ray diffraction.