Evaluation of scratch resistance of diamond-like carbon films on Ti alloy substrate by nano-scratch technique

The nano-scratch tests of diamond-like carbon films on Ti alloy substrate were performed by a Nano Indenter XP(R) system. The scratching processes along with the elasto-plastic deformation were analyzed. It was concluded that the scratch process could be divided into three stages: fully elastic recovery; plastic deformation and delamination of films. When the elastic deformation predominated in the total deformation, the film was not delaminated, but a fish-bone-like trace formed due to the stress concentration at two front edges of the tip. As the plastic deformation amount exceeded the elastic one, the partial spallation of the films was detected. It was determined that the spallation of the films originated right from the fish-bone cracking, and the fish-bone was just a profiling of the Berkovich indenter. It is highlighted physically that the critical loads of the DLC film/Ti alloy substrate system in this study correspond to the point where the amount of the elastic and plastic deformation was about equal. (C) 2002 Elsevier Science B.V. All rights reserved.