2011 Volume 52 Issue 610 Pages 1181-1186
Although a scratch test is commonly used for evaluating the strength of adhesion between a thin film and substrate, the relationship between indentation load and interfacial stress state has not been directly derived. In the present study, three dimensional finite element analyses on a scratch test were performed to clarify the interfacial stress state. DLC-Si and TiN were employed as the film materials. As the substrate material, SUS440 was used. The calculated result was in good accordance with the result of the actual test on the geometry of the scratched groove. From the results of interfacial stress states, the interfacial normal and shear stresses took the maximum at an area inside the lip of the groove where the delamination may first occur in the actual tests. Then, the effect of film material on the interfacial stress state was discussed using this model. The interfacial shear stress was more sensitive to the change in the film material. Finally, the effect of friction between the indenter and the thin film on the interfacial stress is also discussed. The result shows that the interfacial stress state was highly affected by the change in frictional conditions. This indicates that the critical indentation load will fluctuate unless the friction conditions are properly controlled.
