Evaluating Adhesion of Ceramic Coatings by Scratch Testing

Adhesion is one of the most important mechanical properties of ceramic coatings. Scratch testing is considered as a simple and effective method to evaluate adhesion of ceramic coatings. In this paper, the critical normal forces and scratch morphologies for different coating-substrate systems were studied by scratch testing. It is shown that the critical normal force obtained by acoustic emission (AE) signals decreases from 12 N to 7 N when the applied normal force rate increases from 20 N/min to 100 N/min for CVD SiC on C, and the failure area of this scratched sample increases with increasing maximum normal force; Based on scratch morphologies, spallation or delamination can be observed for hard-brittle coatings on glass or metal, while discontinuous or continuous ductile perforation can be observed for ductile coatings on metal; The critical normal force for hard-brittle coatings can be effectively obtained by AE signals.