Densification and mechanical properties of TaC-based ceramics

Densification of TaC was enhanced while the grain growth was suppressed by adding 1 or 2 wt% B4C, which allowed mechanical properties to be analyzed. A relative density of >98% was achieved for TaC with B4C additions by hot pressing at 2100 °C. By comparison, additive-free TaC could be hot pressed to only 94% relative density at 2300 °C. X-ray diffraction analysis identified TaB2 in TaC–B4C ceramics, indicating that a reaction occurred during hot pressing. Mechanical properties including Young's modulus, flexure strength, Vickers’ hardness, and fracture toughness were studied. The Griffith equation was used to calculate critical flaw sizes from measured properties. This analysis combined with observations of fracture surfaces identified surface flaws induced by machining and subsurface impurities picked up during milling as the critical flaws.