박막의 접합력 평가를 위한 압입계면균열의 파괴역학적 분석

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. However, it is valid only when comparing the adhesions in the same materials because material properties are not considered in dP/dc. In this study, therefore, for the more reliable evaluation of adhesion, critical energy release rate was obtained by analyzing the dependency of interface crack on indentation load. Stress field in film could be obtained by analyzing the indentation stress field in substrate and adapting the strain continuity condition at the interface. From the analytical model, released strain energy with film delamination could be formulated. Finally, critical energy release rate could be obtained as the quantitative function of dP/dc and these results compared with those of scratch test. Using this mechanical analysis, the adhesion of diamond-like carbon (DLC) film deposited on AISI D2 steel was evaluated and the effects of factors related to buffer layer on the adhesion were discussed.