Triple-Laser Synergistic Etching: An Effective Strategy for Contour Error Suppression in Diamond Cutting Tool Edges

Diamond tools hold a pivotal position in ultra-precision and micro-machining within the high-tech manufacturing sector, owing to their remarkable cutting performance. However, the manufacturing precision of these tools is often affected by their inherent anisotropy. This study proposes a novel triple-laser combined etching strategy (consisting of CO2, YAG picosecond, and femtosecond lasers) to investigate methods for improving the surface quality of single-crystal diamond tools and reducing the waviness of the cutting edge. During conventional mechanical removal, the variation in hardness across different crystallographic planes of natural diamond induces uneven material removal and cleavage-induced microcracks. Meanwhile, in single-laser processing, the high dissociation energy of sp3 bonds necessitates intense localized energy input, which, coupled with anisotropic thermal expansion, generates non-uniform and significant thermal stresses. To tackle this issue, the proposed multi-laser process employs a hierarchical energy transfer mechanism. Initially, a CO2 laser provides uniform thermal pretreatment, converting the diamond surface into a highly absorptive graphitized (sp2) layer. Subsequently, a YAG picosecond laser achieves selective microstructural refinement, removing coarse graphite and curbing the propagation of microcracks. Finally, a femtosecond laser performs nanoscale precision finishing through multiphoton absorption and non-thermal ablation, stripping the remaining modified layer without causing thermal damage. Comprehensive characterizations suggest that this synergistic approach substantially mitigates the impacts of crystal orientation and suppresses the thermal stress induced by phase transition to a level lower than the fracture strength of diamond. Consequently, the triple-laser etching process effectively suppresses deep microcracks and notably reduces the waviness of the tool cutting edge from 90 nm to 16 nm. Ultimately, the integrated triple-laser strategy provides a highly efficient and precise solution for the fabrication of ultra-precision diamond tools with superior edge integrity.