Ultra-precision cutting characteristics of binderless tungsten carbide by in-heat-process laser-assisted diamond machining

The study systematically investigates the ductile-brittle transition behavior, material removal mechanism, and end-face turning performance of binderless tungsten carbide using in-process-heat laser-assisted diamond machining. Both numerical simulation analysis and experimental cutting experiments were conducted. To ensure that the laser loading condition and energy distribution were consistent with the ray-tracing simulation and spatial power density distribution measurement, a practical thermal simulation model was created with a semicircular Gaussian distribution. This model was then used to study the temperature distribution, and the material`s thermal transient response to laser radiation was also analyzed in detail. The high-temperature nanoindentation revealed increased ductile machinability due to plastic deformation, microhardness reduction, and Young`s modulus decrease at elevated temperatures, providing fundamental support for the ductile-brittle transition behavior. The ductile-brittle transition depth increased by 247.20% compared to conventional groove cutting without laser assistance. The cutting forces during groove cutting decreased gradually with increasing laser power, but excess laser power may cause fluctuations in cutting forces due to surface high-temperature oxidation and potential thermal expansion. The ductile-brittle transition dynamic behavior analysis, based on the discrete wavelet transform algorithm, showed good consistency with the conventional groove profile analysis. The friction coefficient between the tool rake face and chip decreased with increasing laser power, which facilitated improving the tool life. The statistical analysis of end-face turning experiments based on the Taguchi method indicated that laser power was the most significant factor affecting surface quality. The verification turning experiments validated the determined optimal parametric combination. Ultra-high-quality spherical lenses were obtained in ductile cutting mode with slightly less tool wear, a more homogeneous finish (less than 3 nm in Sa), and more outstanding form accuracy (133 nm in PV) compared to conventional turning without laser assistance.