Investigation of microchannels on K24 alloy by femtosecond laser considering the incubation of laser pulse

Microchannels are widely prepared for application in aerospace, refrigeration and air conditioning. To understand the mechanism of material removal, ablation threshold dependent on scanning speed is investigated, which is related to the effective number of laser pulses and the incubation coefficient. For the smaller number of pulses, the material is removed by weak ablation due to vaporization. For the lager number of pulses, the material is removed by strong ablation due to the combined vaporization and phase explosion. To obtain high-quality microchannel on the K24, the surface morphology is measured by scanning electron microscope (SEM). It is found that morphologies of microchannels are strongly dependent on the laser parameters, especially the laser power and scanning speed have the strongest effect on the morphology. Meanwhile, the oxidation reaction is found on the zone of microchannels. Furthermore, the geometry of microchannel is predicted and compared to that of experimental measured. The results indicate that the predicted geometry is well agreement with those experimental results. Finally, the relationship between material removal rate and laser parameters is investigated. This work not only promotes the recognition of the mechanism of material removal by femtosecond laser on high-temperature alloy, but also presents effective guidance for achieving high-quality machining of microchannel.