Interface delamination is the major failure mode of diamond-coated carbide tools in machining. On the other hand, coating cracking is possibly accompanied during a tribological process that induces the delamination phenomenon. However, such an influence between the two failure behaviors has not been investigated in a quantitative way to better understand and design diamond coating tools.

In this study, a three-dimensional (3D) indentation model combining cohesive interactions and extended finite element method (XFEM) was developed to investigate the diamond-coating, carbide-substrate interface behavior with the incorporation of coating cracking. The interface interaction was based on a cohesive zone model (CZM) with a bilinear traction-separation law. XFEM was applied to the coating domain to model cracking in the diamond coating with a damage criterion of the maximum principal stress. Deposition stresses were also included to investigate their effect on the coating delamination and fractures. The model was implemented in finite element (FE) codes to analyze the cone crack in brittle coatings, as well as the interface delamination of diamond coated carbide tools. The XFEM model was validated by the indentation testing data from literature in crack initiations and propagations in brittle materials. FE results from the indentation on diamond-coated tools show that the interface delamination size and the loading force become smaller when coating fractures are incorporated in the model, and the deposition stresses will increase the initial crack radius as well as the critical load for delamination in diamond coatings.

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