The chemical reactivity of CrN, ZrN, TiCxN1-x and naCo (R) PVD coatings on a WC-Co cemented carbide substrate with steel has been evaluated by means of the static interaction couples technique. Diffusion experiments with coated and uncoated tools were carried out at 900, 1100 and 1300 degrees C in order to establish the maximum temperature at which the sub strate-coating-workpiece combinations are chemically stable. Computational equilibrium thermodynamics was used to identify the interaction products formed at elevated temperature and the chemical solubility of the different coating materials into iron. A metallic (Fe, Co) fee solid solution was identified at the steel side of the interface from 1100 degrees C on for all the coated tools and from 900 degrees C for the uncoated carbide. In addition to this interaction product, the eta-carbide was identified at 1300 degrees C on the WC-Co side of the interface. Both of the experimental findings and thermodynamic equilibrium solubility calculations demonstrated that the PVD-coated WC-Co tools exhibit a lower chemical reactivity with respect to the Uncoated tools. (c) 2006 Elsevier B.V. All rights reserved.