In Situ Preparation of Micro–Nano Tantalum Carbide Ceramic

The microstructure and mechanical properties as well as the formation and morphological evolution mechanism of micro–nano TaC carbide prepared by an in situ casting–heat treatment reaction and chemical extraction method have been investigated. The size of the TaC particles was approximately 50–900 nm. The formation process and mechanism included nucleation growth of TaC grains and a diffusion-type solid-phase transition. Due to the “freezing” of the microstructure, the movement of the grain boundaries is inhibited, resulting in ultrafine TaC ceramic particles. The TaC particles preferably grow as cubes enclosed by {100} facets with minimized total surface free energy, indicating that both the intrinsic lattice structure and the growth conditions determine the final morphology of the TaC particles. In addition, the hardness and elastic modulus of the TaC ceramic were found to be 26.5 ± 0.4 GPa and 506.4 ± 5.8 GPa, respectively. Moreover, the fracture toughness was found to be 3.8 ± 0.1 MPa m1/2. The toughening mechanism of the TaC ceramic layer includes crack deflection and crack bridging.