Properties of Ultrafine WC-Co Cemented Carbide Prepared from Tungsten Carbide Nanopowders through a Two-Step Carbonization Method

The effects of a two step carbonization method on properties of tungsten carbide nanopowders and the cemented carbides have been studied. It is shown that the grain aggregation and abnormal coarse grains are mainly due to the sintering combination of agglomerated Particles of tungsten or tungsten carbide nanopowders during carbonization process and incomplete carbonization is attributed to the low carbonization temperature. The two step carbonization method (the first step carbonization temperature 1120 degrees C, and the second step carbonization temperature 1180 degrees C) can effectively inhibit the sintering combination phenomenon between nanoparticles, and can carburize the tungsten nanopowders fully. Therefore homogenous tungsten carbide nanopowders are obtained and the content of W2C of the nanopowders is only 0.5%. Microstructures of ultrafine WC-Co sintered composites prepared from the powders through the two step carbonization method are uniform; the properties of the alloy are excellent, and the HRA hardness and bending strength are 93.7 and 4380 MPa, respectively.