Metal-ceramic interfacial fracture resistance using the continuous microscratch technique

To investigate the adhesion of thin films to substrates, continuous microscratch tests were carried out on carbon or nickel thin films bonded to silicon, NiO, or Al₂O₃ substrates. In the present study, continuous microscratch experiments were carried out by driving a conical diamond indenter into the sample at a rate of 15 nm s^-1 and across the sample surface at a rate of 0.5 μm s^-1, until a load drop occured, indicating film delamination. The critical load for film delamination provides a qualitative measure of the adhesion strength of the bi-material system. From the area of the debonded film and the critical load to failure, a quantitative measure of the strain energy release rate and the interfacial fracture resistance of the bi-material systems, was calculated using a model developed in a previous paper. The strain energy release rate and the interfacial fracture toughness were in the range 0.05-0.5 J m^-2 and 0.1-0.55 MPa m 1 2 respectively. These values are in reasonable agreement with those determined by other methods for metal-ceramic systems. In general, the fracture resistance for brittle films was found to be much larger than that for ductile films. Preliminary investigation of the contributions of film and substrate modulus to the work of adhesion indicate that the work of adhesion increases non-linearly with the moduli.