Sintering Behavior and Mechanical Properties of Dispersed-Reinforced Fe-TaC Composites Produced by High Energy Ball Milling

Abstract

In this study, a high-melting point element, tantalum carbide (TaC) was added to improve the mechanical properties and the oxidation/corrosion resistance of Fe. The Fe-TaC composites were synthesized by high energy ball milling for the mechanical alloying of the non-equilibrium phase (Fe-Ta) and the homogeneous dispersion of TaC. Fe-TaC composite samples were fabricated using 5, 10, and 20 wt.% TaC. The ductile particles (Fe) got harden and the brittle particles (TaC) were uniformly dispersed, while facilitating short-range diffusion in the ductile matrix by the high energy ball milling method. Spark plasma sintering was performed at a sintering temperature of 850 oC and pressure of 60 MPa. As the TaC contents increased, the sintering exponential (m) increased. A higher ‘m’ value indicates a lower magnitude of shrinkage, by decreasing the lattice and grain boundary (G/B) diffusion path between the pores and particles. The hardness increased from 128.9±10.4 to 444.2±20.6 kg/mm<sup>2</sup> as the grain size decreased from 5.13 to 3.99 μm. This enhancement is attributed to the Hall-Petch relationship and dispersion strengthening effect. The mechanical properties of the sintered bodies were studied to evaluate how the different TaC content affect their characteristics. In addition, oxidation resistance increased with increasing TaC contents. It was considered that the local oxidation resistance based on the formation of an oxide layer of TaO and Fe<sub>2</sub>O<sub>3</sub>.