ADHESION TESTING BY THE SCRATCH TEST METHOD - THE INFLUENCE OF INTRINSIC AND EXTRINSIC PARAMETERS ON THE CRITICAL LOAD

The aim of this paper is to discuss the influences of the intrinsic and extrinsic parameters on the critical load, in connection with the scratch test, to allow an improved interpretation of the critical loads and the coating adhesion evaluation. The samples used for this study consisted of TiC-, Ti(C, N)- or TiN-coated steels or cemented carbides, deposited by chemical vapor deposition (CVD) and physical vapor deposition (PVD) techniques. First, the influences of the following intrinsic parameters, loading rate, scratching speed, tip radius and wear rate, and the following extrinsic parameters, substrate hardness, coating thickness, substrate and coating roughnesses, friction coefficient between tip and coating and the friction force in the scratching direction have been examined. Using the reported experimental results, it was possible to put forward some empirically desired relationships. In the second part of this paper, there is the presentation of a theoretical approach based on the model of a static spherical indenter pressed on the coating surface.