Tantalum carbides/boride composite were synthesized by spark plasma sintering (SPS), using the powder mixtures of TaC and B4C as the starting materials. In this work densification, phase formation, microstructures, and mechanical properties of the materials were investigated. The densification of tantalum carbide (TaC) was enhanced by adding 2.0 wt% B4C, reaching 97% relative density by SPS at 1900 oC using a 30 MPa applied pressure. X-ray diffraction analysis identified two phases, TaC and tantalum diboride (TaB2), with no peak shifts, indicating a solid solubility was not significant at these temperatures. Densification of TaC was enhanced while the grain growth was suppressed by adding 2 wt% B4C, which allowed mechanical properties to be analyzed. Relative density of > 97% was achieved for TaC with B4C additions by SPS at 1900 oC. By comparison, additive-free TaC could be sintered to only 76% relative density at 1900 oC. The effect of B4C addition and sintering temperature on hardness measured by microhardness has been studied. Hardness of samples contain 2.0 wt% B4C was 15.10 vickers.

Keywords: Tantalum carbide/boride, Microstructure, Microhardness, densification, Spark plasma sintering.