AbstractThe adhesion of thin ceramic films to metal substrates is an important issue in a wide variety of technological areas; one of which is the corrosion of metal alloys at high temperature. Consequently, there is great interest in exploring the measurement of adhesion between ceramic films and metal substrates and the factors that control such adhesion. In this study, five methods for assessing the adhesion of thermally grown oxide scales to their substrates have been evaluated to establish their relative usefulness. Simple, well characterised model oxidation systems (high purity nickel, Ni–0·1 wt-%Cr, and Ni–0·1 wt-%Al alloys) have been used. The experiments showed that practical adhesion was measured most successfully using a double bending beam configuration and quantified in terms of the normal applied stress for catastrophic interfacial failure. Although the more convenient standard scratch test gives only semiquantitative results, these are nevertheless useful for comparisons within a given system. None of the techniques was capable of measuring the fracture toughness of the interface. The degree of practical adhesion of the oxide scales was found to decrease in the substrate order: high purity nickel>Ni–0·1Al>Ni–0·1Cr. The practical adhesion to the two alloys was sensitive to oxide thickness and there is a critical thickness (about 1·7μm for Ni–0·1Cr and 4·8μm for Ni–0·1Al) above which the practical adhesion is very low. This critical condition is probably the result of relaxation of residual compressive stress in the oxide by buckling of the scale.MST/1467