| Indentation cracking test has been used to evaluate the adhesion of wear-protective coatings such as diamond film. This test can induce interface crack by applying indentation load to the film. A reciprocal of the rate of change of interface crack radius with indentation loads(dP/dc) has been generally used as the qualitative criterion of the adhesion. This concept is, however, valid only when comparing the adhesion in the same materials because the material properties are not considered in dP/dc. In this study, therefore, for the more reliable evaluation of adhesion, the critical energy release rate was obtained by analyzing the dependency of interface crack on indentation load. Stress fields in film were from the indentation stress field in substrate using the condition of strain continuity at the interface. From the analytical model, the strain energy released by film delamination was formulated. Finally, the critical energy release rate was obtained as the quantitative function of dP/dc and was compared with the results from scratch test. Using the proposed analysis, the adhesion of diamond-like carbon(DLC) film deposited on AISI D2 steel was evaluated. |
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