Improving WC-Co coating adhesive strength on rough substrate: finite element modeling and experiment

Abstract The adhesive strength in a coating-substrate system is of primary importance for the coating lifetime in service. However, the underlying mechanism is not fully understood due to the complex internal structure of composite coatings. In this study, the effect of substrate roughness on the adhesive strength of WC-Co coatings was investigated by experiment and simulation. Results show that the adhesive strength is significantly affected by the roughness. In the case of the Ra＜2 μm, the adhesive strength is approximately 35‒46 MPa. When the Ra is 4 μm, the adhesive strength increases to nearly 60 MPa. A finite element model was developed to correlate the roughness with adhesive strength. It is found that the predicted values are well consistent with the experimental data. In addition, with the increase of the roughness, the residual stress would be changed from concentrated state to widespread state, which decreases the critical stress to result in crack propagation. That’s why a larger roughness can cause a higher adhesive strength. This study gives understanding on the mechanism of adhesive strength affected by roughness, which contributes to the parameter optimization with better performance.