Effects of Carbon Addition on Microstructures and Mechanical Properties of Binderless Tungsten Carbide

Binderless tungsten carbide (WC) with added carbon was sintered at 1800°C using a resistance-heated hot-pressing machine. Dense binderless WCs were obtained in the range from 0.25 to 0.3 mass% C, consisting of only a WC phase. The constituent phase transition with increasing carbon addition was WC + W2C, WC alone, and WC + residual C. Very fine WC grains were formed in the presence of W2C below 0.25 mass% C. When binderless WCs consisted of a WC single phase, larger WC grains were observed. While a high hardness value, more than 23.9 GPa, was measured for binderless WCs below 0.20 mass% C, the hardness decreased markedly in the range from 0.25 to 0.3 mass% C, corresponding to significant WC grain growth. A Hall–Petch-like relationship was confirmed between the hardness value and the grain size for dense binderless WC.