New adhesion measurement technique for coated cutting tool materials

Adhesion properties of wear resistant coatings on cutting tool materials are essential to their performance in technical applications. It is therefore necessary to characterize the coating adhesion by an appropriate measurement technique which reveals both critical adhesion values as well as information on time dependent debonding. In particular, a quantitative and reproducible technique is required rather than largely qualitative methods such as indent or scratch tests. In addition, for multilayer coatings, the location of the weakest interface is required to facilitate improvement of interfacial integrity. Accordingly a sandwich double cantilever beam (DCB) test was developed and used to measure the adhesion properties of coatings on cermets. Additionally, the structure of the coatings in the as fabricated state and after mechanical testings were characterized by optical microscopy, SEM and TEM. With quantitative adhesion measurements and investigations of the interface microstructure, a comprehensive characterization of coating adhesion on cutting toolmaterials was achieved.