High pressure - Low temperature sintering of tungsten carbide ceramics

Pure tungsten carbide is a very hard and corrosion resistant material. Its various applications, such as wear parts, water-jet nozzles or pressing tools for forming glass lenses attract toolmakers and scientists alike. Due to the absence of any metallic binder or sintering aides, sintering of pure binderless tungsten carbide is normally done at high temperatures at around 2000 °C. In order to limit grain growth, sintering at lower temperatures is preferable. Two different pressurized sintering techniques were used to densify a nanoscaled tungsten carbide powder (DBET=60 nm) at low temperatures: a conventional SinterHIP furnace with an Ar pressure of 10 MPa (100 bar) and a special high pressure SPS furnace, enabling a pressure of 300 MPa. Sintering temperature was between 1200 °C and 1400 °C. The development of density and microstructure was correlated with the chemical processes occurring during sintering. Grain growth was studied using XRD and Rietveld techniques.