Properties of sintered alumina reinforced with niobium carbide

The presence of carbide or nitride particles in Al 2O 3-based composites may produce a pinning effect and inhibit the grain growth of the matrix, which might significantly contribute to the final performance of the composite. Fracture toughness, mechanical strength and wear resistance have been particularly improved by the dispersion of hard particles. This work has the purpose to investigate the potential use of NbC as alumina reinforcing material, as an alternative to other carbides such as TiC, WC and (W, Ti)C. Alumina was mixed with a constant 30 wt.% of carbide in a ball mill, uniaxially hot-pressed at 1600 °C and 20 MPa in an inert atmosphere, and characterized. X-ray diffraction revealed that alumina and the added carbide were the only crystalline phases present and no oxidation products were detected. The increase in fracture toughness likely is the result of crack deflection, triggered by carbide particles at the alumina grain boundaries. The results obtained in this work show that alumina reinforced with NbC is a composite material with properties comparable to those of alumina reinforced with WC, TiC or (W, Ti)C, making NbC a good reinforcing material.