Improvement of the compressibility of cobalt powders for the cemented carbide industry

The compressibility of cemented carbide granules is a very important factor to ensure reliability and repeatability of the pressing process. A main aim is to produce granules that can be pressed to compacts which exhibit a high density with a uniform distribution. This will result in less shrinkage and warpage during sintering. In the presented work it is shown that a correlation between the compressibility of the raw material powders (WC and Co) and the resulting cemented carbide granules exists. Furthermore cobalt powders with different characteristics were investigated in detail regarding the compressibility. The results show how the compressibility of cobalt powders can be improved by varying the particle distribution, the agglomeration and morphology. Subsequently also the resulting cemented carbide granules which include these Co powders showed a higher compressibility. On the other hand the oxygen absorption of the cobalt decreased the compressibility of the powder and the resulting cemented carbide granules.