Technique Research Of Femtosecond Laser Pulses For Drilling The Shaped Micro-hole Of Turbine Blades

The function of the new type of aviation engine totally depends on the quality andthe shape of the film cooling micro-holes on the turbine blade. Film coolingmicro-holes have a significant effect on the index of aviation engine, which is crucialfor the performance of the aviation engine. Because of the distinct cooling effect of theshaped micro-hole of turbine blade on the aviation engine, the shaped hole is gainingmore and more attention from aviation equipment suppliers. Currently, the shapedholes are machined by electric spark, electro-stream techology and longer laser pulsesetc. These methods have caused several unexpected quality problems such asformation of recast layer, ripples, thermal effect and irregular hole shapes.Femtosecond laser pulses drilling has distinct strong points against electric spark andlonger laser pulse processing techologies. Such advantages are no recast layer, nothermal effect, no micro crack, high precision, and high processing efficiency.Owing to the much lower pulse duration and very high photon densities offocused femtosecond laser pulses, femtosecond laser has many advantages of lowerthreshold energies for ablation, mimimum thermal diffusion in pulse duration to reduceheat affected zone, non-selective on materials and so on. Femtosecond laser proceesingtechology is the representative of the hyperfine cold manyfacturing techology, also it isa new direction and the main develop trend of the advanced manufacturing techology.In this paper, we came up with an effective experimental proposal and designed aset of processing devices using femtosecond laser pulses for drilling the shapedmicro-hole of turbine blades and demonstrate that femtosecond laser is truly anexcellent and universal tool for microfabrication. The comopsite five-axis motionplatform, combined with the laser shutter timing control process makes it possible toachieve the shaped micro-hole. We investigate the mechanism of the femtosecond laserinteraction with materials. The process of femtosecond laser interaction with materialsis a series of very complex physical process, in which non-melt domin the process. When femtosecond laser pulse beam propagating in the medium, achievable non-lineareffects easily generate. In addition, the mechanism of the femtosecond laser interactionwith metals, dielectrics and semiconductors are investigated. There are various offactors which affect the laser pulses drilling micro-holes, not only the laser pulseenergy, pulse width but also the quality of the laser beam and the waveform of pulses.In this contribution influences on drilling efficiency and hole quality by differentprocess parameters such as laser pulses width, repetition, and fluence etc are presentedand disscussed respectively. Femtosecond laser processing technology is very complex,and the task is very difficult. We need to continue to further optimize the laserprocessing parameters, improve and perfect process in order to realize the laserhyperfine processing.