A model for the hardness of cemented carbides

A new model for the hardness of cemented carbides is proposed. The model is based on the main assumption that very thin binder layers (a few atom layers) confined between hardphase grains are forced to behave mechanically as the confining material. When increasing the binder layer thickness, the influence from the hardphase will decline, following an exponential relationship. This model has the advantages over current models that it predicts the hardness from data on carbide grain size and volume fraction only, without the need for the laborious carbide contiguity value. It also covers a wider range of carbide grain sizes and binder volume fractions than do the current models. The model has been verified on a very wide range of cemented carbide compositions, covering a hardness interval of 800–2400 Vickers. Throughout this interval, the calculated hardness values agree to within 15% to the measured values. This makes the model a useful tool in the development of new WC–Co grades, for the interpretation of wear results and for estimating grain size and cobalt volume fraction values.