Mechanisms of femtosecond laser ablation of brazed diamond tools: A two-temperature model for multi-material interfaces and experimental validation

Although the precision dressing of diamond abrasive tools using ultrafast lasers has attracted considerable attention, achieving efficient and low-damage dressing remains a critical bottleneck due to the highly complex interactions between the composite abrasive materials and the ultrafast laser beam. To investigate the interaction mechanisms between femtosecond laser pulses and brazed diamond tools, a two-dimensional axisymmetric two-temperature model was developed to simulate the thermal behavior at the interface between single-crystal diamond (SCD) and the BNi-2 nickel-based brazing filler metal during femtosecond laser ablation. The model incorporated multiphoton ionization and avalanche ionization to describe the generation and evolution of the free electron density in SCD and calculated the resulting transient changes in its optical properties. To validate the effectiveness of the two-temperature model, single-pulse femtosecond laser ablation experiments were conducted on BNi-2 and brazed diamond workpieces at various laser fluences. Results indicated that femtosecond laser irradiation induced a sharp increase in the free electron density within the SCD, leading to pronounced nonlinear changes in its optical properties. The marked mismatch in thermophysical properties and ablation thresholds between SCD and BNi-2 resulted in distinct thermal and ablation responses. The large temperature gradient across the interface drove intense heat transfer, thereby intensifying localized ablation near the interface. The predicted ablation thresholds agreed well with the experimental values. This study provides a theoretical basis for understanding the differences in ablation thresholds and thermal responses between SCD and BNi-2 under femtosecond laser irradiation. These findings provide guidance for the selective laser removal of heterogeneous materials and support the high-precision, controllable laser dressing of brazed diamond abrasive tools.