Ultrashort pulsed (USP) laser processing of binderless nanopolycrystalline diamond (NPD)

Ultrashort pulsed (USP) laser machining is a promising approach for processing binderless nanopolycrystalline diamond (NPD), which combines isotropic ultra-high hardness and high thermal stability. This study systematically investigates USP laser ablation to identify suitable conditions for advanced microtool fabrication. The influence of pulse duration ( τ ), wavelength ( λ ), fluence ( F ), pulse frequency ( f ) and pulse and track overlaps ( O x , O y ) on orthogonal and quasi-tangential ablation of NPD was evaluated. The single-pulse ablation threshold ranged from 1.56 J / cm 2 for green fs irradiation to 8.82 J / cm 2 for IR ns irradiation. In orthogonal ablation, increasing f improved ablation efficiency under high-fluence conditions, with IR fs giving the highest material removal, while green fs at low frequency provided the best compromise between low roughness and high efficiency. In the overlap study, O x = 0.6 and O y = 0.8 yielded the lowest surface roughness. For quasi-tangential machining, an optimum parameter window was identified with R a = 13 nm and S a = 51 nm . Finally, NPD micro milling tools with sharp cutting edges ( r ϵ = 1.03 ± 0.13 μ m ) and low surface roughness were successfully fabricated. • Binderless nanopolycrystalline diamond showed the lowest ablation threshold under green femtosecond laser irradiation and the highest threshold under infrared nanosecond irradiation. • In orthogonal machining, green femtosecond irradiation at low frequency provided the best balance between smooth surfaces and efficient material removal, while infrared femtosecond irradiation at high frequency produced the highest removal rates. • A narrow optimum process window was identified for quasi-tangential machining, yielding very low surface roughness and high surface quality on cylindrical binderless nanopolycrystalline diamond. • Micro milling tools were successfully fabricated by combining orthogonal ablation for flute generation with quasi-tangential ablation for tool shaping, producing sharp cutting edges and low surface roughness in binderless nanopolycrystalline diamond.