A NUMERICAL STUDY OF INTERFACE BEHAVIOR OF DIAMOND COATED CUTTING TOOLS

Interface delamination is the major weakness limiting diamond coating tool performance in machining. Thus, quantitative characterizations of the interface behavior are important to better understand and design diamond coating tools. In this study, we attempt to apply a cohesive zone model to investigate the coating-substrate interface behavior. The cohesive zone model is based on the traction-separation law with three characteristics determined from the material fracture properties. The model is implemented in finite element codes to simulate the indentation process and to analyze the delamination size of diamond coated tungsten-carbide substrates. The simulation results indicate the following. Increasing the coating elasticity will reduce the delamination size due to the delay of substrate yielding. On the other hand, increasing the magnitude of coating residual stresses (compressive) will marginally increase the delamination sizes. Moreover, a thicker coating tends to have greater resistance to the interface delamination.