• Llanes, Luis
• Mestra, A.
• García-Marro, F.
• Maweja, Kasonde
• Kanyanta, Valentine
• Ozbayraktar, S.

Abstract

he tolerance to contact damage of polycrystalline diamond (PCD) composites is investigated. Three different PCD grades are considered. Contact damage is extrinsically introduced by spherical indentation techniques, an approach well-established to evaluate damage tolerance issues in other hard materials. Such damage is induced on the surface of polished specimens, under both monotonic and cyclic loading conditions, and is characterized by optical and scanning electron microscopy. Residual strength is used as discriminative parameter for evaluation of damage tolerance. Hence, non-indented (reference) and indented specimens are fractured by means of biaxial ball-on-three-ball flexure testing. Results show that tolerance to contact damage is dependent on the microstructural characteristics of each PCD grade. Hence, although fine PCD grade exhibits the highest reference strength, corresponding indented specimens show pronounced fracture resistance decay for relatively high applied loads or number of cycles. On the other hand, the bimodal and coarse PCD variants are found to be more tolerant to contact damage, i.e. fracture strength shows only slight changes as cracks are introduced. The trends discerned are discussed on the basis of relative discontinuous character and sharpness of the induced damage, as well as effective depth of corresponding cracks, all of them directly dependent on the PCD microstructure assemblage.

Topics

• impedance spectroscopy
• microstructure
• surface
• scanning electron microscopy
• crack
• strength
• composite