Investigation on stress distribution and wear behavior of brazed polycrystalline cubic boron nitride superabrasive grains: Numerical simulation and experimental study

The polycrystalline cubic boron nitride (PCBN) superabrasive grains, which are comprised of microcrystalline CBN particles and AlN ceramic binder, have a distinguished advantage in self-sharpness during grinding by means of controllable fracture wear. The present work intends to clarify the mechanism of grain fracture based on the analysis of brazing-induced residual stress and the resultant stress in grinding; as such, the grain fracture wear could be predicted and controlled effectively. A finite element model based on Voronoi tessellation method has been first established for PCBN grains. The effects of embedding depth, volume fraction, and grinding loads on the stress distribution within PCBN grains are discussed. It is found that the distribution patterns of microcrystalline CBN particles generally have less influence on grain fracture. Large tensile stress is produced at the interfaces of microcrystalline CBN particles, AlN ceramic binder and Ag-Cu-Ti filler. Particularly, the largest tensile stress is generated near the grain vertex in the case of the embedding depth of 50%, volume fraction of 80%, and uncut chip thickness of 0.6 μm. The simulation results are verified experimentally through characterizing the wear topography evolution of brazed PCBN grains in grinding.