Hot pressing of tungsten carbide with and without sintering additives

This study presents the results of investigations concerning hot-pressing of submicron WC powders without sintering additives and with the addition of carbon or tungsten or both elements simultaneously. Dense polycrystals of diverse microstructures and phase compositions were obtained. Attempts were made to correlate a microstructure and phase composition of sinters with their thermal and mechanical properties. It was found that the presence of graphite nanolayers on grain boundaries in WC sinters with the addition of carbon favourably influences their thermal conductivity. All produced polycrystals are characterised by a high fracture toughness. The smallest scatter of KIc results is observed for compositions activated by a carbon addition. The presence of the graphite nanolayers as well as grain size in WC sinters with carbon additions reduce the polycrystal hardness. All WC polycrystals, regardless of introduced additives, are characterised by high bending strength and by high values of the Young and Kirchoff moduli. The tested polycrystals are not suitable for machining carbon steel of C45 grade.