| Nickel-based superalloy material has the advantages of good heat resistance,corrosion resistance and high fatigue strength,and is the most widely used material for aero-engine turbine blades.At present,aero-engine turbine blades are mainly made of nickel-based superalloy materials and gas film cooling technology to improve the high temperature resistance of turbine blades and ensure their continuous and reliable work in high temperature and pressure environments.Based on the defects of recasting layer and micro-crack in traditional laser machining of gas film holes,a new ultrasonic assisted laser chemical composite machining technology is proposed in this paper.This new composite machining technology combines the advantages of laser chemical composite machining and ultrasound-assisted laser machining: the slag and recast layer generated in the process of laser machining can be removed by using the processing advantages of laser,such as high efficiency,high precision and non-contact,combined with the vibration and cavitation effect caused by the addition of ultrasonic.At the same time,the high temperature generated by the laser can improve the reaction rate of the chemical liquid and the slag,promote the reaction between the chemical liquid and the recast layer and the oxide layer formed in the laser processing process,and improve the quality of the micropores processed by the laser.First of all,this paper summarizes the development status of laser machining gas film holes,and analyzes the research status of laser composite machining microholes,such as water-assisted laser machining microholes,chemical-assisted laser machining microholes,and ultrasound-assisted laser machining microholes.The mechanism of laser machining microholes and laser chemical compound machining microholes is introduced.On this basis,the mechanism of ultrasound-assisted laser chemical compound machining is studied.Secondly,the influence of the concentration and ratio of chemical liquid on the surface quality of laser chemical compound machining micropores was analyzed,the best ratio of chemical liquid was selected,and then it was proved that the laser chemical compound machining method could improve the quality of micropores.The influence of the air,water and chemical solution on the surface morphology,hole depth,aperture and roundness of the micropores was compared and analyzed through experiments of laser machining micropores in air,water and chemical solution.The results show that,compared with the micropores processed by laser in air or laser in water,there is almost no recasting layer accumulation,and the oxides and slag particles attached to the inner wall of the micropores are dissolved and eliminated.Thirdly,the influence of the addition of ultrasound on the quality of microholes in laser machining was studied.By comparing the micro-hole experiments of laser underwater machining with and without ultrasonic assistance,the results show:slag accumulation was found in the orifice and inner wall of the microholes obtained without ultrasound,while the inner wall of the microholes obtained with ultrasound was smoother,with almost no debris attached to the melt,and the roundness of the orifice was better,which proved that the quality of laser microhole processing could be improved by ultrasound-assisted addition.Finally,on the basis of proving that the quality of microholes can be improved by both laser chemical compound machining and ultrasound-assisted laser machining,the ultrasound-assisted laser chemical compound machining method is proposed,and the ultrasound-assisted laser chemical compound machining process is studied.Along with the increase of laser power,the ultrasonic assisted laser chemical compound machining method of micro hole hole depth and diameter are increased obviously,when the laser power up to 50 w,using the ultrasonic assisted laser chemical compound machining method can get better surface quality of the hole,but when sustained increases to about 60 w power of microporous orifice deposits are difficult to remove,the aperture morphology is not good,so the laser power of the composite machining method should be controlled at about 50 W.It is also found that with the increase of scanning speed,the number of laser pulses in the machining area will decrease directly.Therefore,when using ultrasound-assisted laser chemical compound processing technology to process microholes,the laser scanning speed should be controlled at about 20mm/s for the best effect,and the morphology of microholes obtained is good,and the roundness is relatively high,and the heat affected zone of the laser is relatively small. |
PDF Full Text Request