Hot-pressing Sintering and Characterization of a High-Strength TiB2-TiN-Al0.3CoCrFeNi Cermet Composed of Ultrafine-Grained by In-Situ Reaction Synthesis

The TiB2-TiN-HEA 2-TiN-HEA cermet materials were synthesized in-situ reaction hot-pressing sintering at 1450 degrees C for 1 h, utilizing Ti, BN, and Al0.3CoCrFeNi 0.3 CoCrFeNi high entropy alloys (HEA) as starting materials. The thermodynamic characteristics of the reaction system and the phase structure, microstructure, and mechanical properties of Ti-BN, TiHEA, BN-HEA, and Ti-BN-HEA were investigated. The results demonstrate that in-situ reaction hot pressing sintering phases include TiN, TiB2, 2 , and FCC structural. The synthesis of TiB2 2 involves the diffusion of B to TiB and the subsequent combination of Ti and B in solution. Conversely, the formation of TiN consists of the diffusion of N to TiN0.3 0.3 and Ti2N, 2 N, as well as the subsequent combination of Ti and N in solution. The TiB2-TiN-HEA 2-TiN-HEA cermet exhibits a relative density of 99.1%, Vickers hardness of 18.91 GPa, flexural strength of 721 MPa, and fracture toughness of 7.61 MPa m 1/2 . The high strength of cermet was due to a combination of factors, including the synergistic effect of high compactness of composites, reinforced interfacial strength with HEA, reinforcement of fine-grains and TiB2 2 rod-like grains, crack bridging and deflection, and transgranular fracture.