Influence of Carbon Content on the Microstructural Evolution and Mechanical Properties of (TiZrHfNbTaCr)C <i> _x </i> Carbides

ABSTRACT (TiZrHfNbTaCr)C x ceramics with different carbon contents were fabricated via carbothermal reduction (CTR) combined with spark plasma sintering (SPS) at 1900 to 2100°C. The effects of carbon content and sintering temperature on Cr solubility, as well as the microstructure and mechanical properties, were systematically investigated. At 1900°C, samples with low carbon contents form a single‐phase solid solution with homogeneous elemental distribution; however, the Cr content within the grains (∼1 at.%) is significantly lower than that in samples with high carbon contents. In contrast, Cr 3 C 2 at triple junctions of grain boundaries is detected in samples with high carbon contents. With increasing sintering temperature, the solubility of Cr increases (4 at.%) and the elemental distribution becomes more uniform, although Cr still shows a tendency to segregate along grain boundaries. Under conditions of lower carbon content and sintering temperature (1900°C), the ceramics exhibit excellent comprehensive mechanical properties with the Vickers hardness of 22.2 GPa, flexural strength of 536 MPa, and fracture toughness of 4.32 MPa·m 1/2 . Correspondingly, the dominant fracture mode transitions from transgranular to intergranular fracture.