Ultrashort pulsed laser drilling and surface structuring of microholes in stainless steels

Microholes for the production of gasoline direct injection nozzles were obtained by ultrashort pulsed laser machining in martensitic stainless steels. The inner surface analysis was carried out by a specifically conceived Scanning Probe Microscopy instrument and revealed the presence of periodic surface microstructures whose formation was studied as a function of process parameters (pulse energy, repetition rate, rotational speed, drilling strategy). Experiments demonstrated that geometrical features of the microstructures can be varied by a proper parameter selection and open the perspective for an optimized process enabling a reduction of coking accumulation during service life and a more effective atomization of the fuel jet.