Niobium carbide is a green cubic crystal with metallic luster and belongs to the sodium chloride type cubic crystal system. The relative density is 8.47, the lattice constant a=0.447nm, and the melting point is 2300°C. Microhardness>235Gpa (>2400kg/mm2), harder than corundum. Elastic modulus 338000N/mm2, thermal expansion coefficient 6.65×10-6/K, thermal conductivity 14w/(m.K), heat of formation -140.7kJ/mol, specific heat capacity 36.8J/(mol.K), resistivity 35μΩ.cm. Insoluble in water and in all acids except a mixture of nitric acid and hydrogen fluoride. It is stable at 1000-1100°C, and rapidly oxidizes to niobium pentoxide at temperatures above 1100°C. Niobium carbide is easy to melt in titanium carbide, zirconium carbide, tungsten carbide and other compounds, and together form an isomorphous solid solution mixture.
