Theoretical and experimental insights into microstructure effects on WC machinability

High requirements on surface roughness from the optics industry pose great challenges to the machining of cemented carbide WC-Co and binderless WC. The mechanical machining of WC (Co) is inevitably influenced by its microstructure characteristics, which govern the formation of machining-induced micro-defects. To address these challenges, this study establishes theoretical models to predict the occurrence of micro-defects and the corresponding critical conditions. WC (Co) samples with different microstructures are characterized, and the connection between the mechanical properties and microstructure is revealed through different indentation techniques. Subsequently, taper cutting experiments are conducted on the different samples to identify micro-defects, corresponding critical uncut chip thickness, and to validate the theoretical models. Finally, diamond turning is employed to achieve the final surface under the predicted conditions. The results indicate that the primary micro-defects affecting surface quality are WC grain fracture and detachment, and the proposed models effectively predict their occurrence for two samples. Suppressing these micro-defects significantly improves surface quality, although the anisotropy of WC grains and pits remains a challenge. These findings offer a theoretical and experimental framework for understanding and optimizing the machinability of WC-based cemented carbide.