Application Of Laser Cleaning In Aircraft Parts Repair

Aiming at the technological requirement of surface cleaning in aero-engine parts repair,we studied the process of fiber pulse laser cleaning for oil filter and nozzle,and made some speculation on its mechanism.By analyzing the structure of parts and cleaning requirements,the suitable laser close-packed mode in laser cleaning is determined.According to the predecessor’s conjecture of cleaning mechanism,a reasonable conjecture was made and verified by experiments,and the direction for laser cleaning of the same pollutant was put forward.In the experiment,gradient experiments were carried out on the parameters of laser type,laser power,laser frequency and scanning speed used in laser cleaning of aero-engine surface pollutants.The optimum parameters for oil filter cleaning and nozzle cleaning were obtained.Oil filter cleaning is most suitable for cleaning with nanosecond laser,the optimum technological parameters are 20 W laser power,66 kHz laser frequency,400 ns pulse width,5000mm/s scanning speed,0.03 mm line spacing and one-way filling.Femtosecond laser is most suitable for fuel nozzle cleaning.The optimum process parameters are laser power of 8W,laser frequency of 200 kHz,pulse width of 350 fs,scanning speed of 5000mm/s and line spacing of 0.015 mm,also one-way filling.By comparing the performance and action mechanism of nanosecond laser and femtosecond laser in cleaning process,we draw a preliminary conclusion that nanosecond laser is more suitable for cleaning grease pollutants with strong binding force and thicker thickness because of its advantage in heat input.Femtosecond laser is more suitable for carbon-deposited pollutants because of its high peak power,strong impact and low heat input.In addition,nanosecond laser is relatively insensitive to defocus,which is more suitable for laser cleaning of parts with high or low tolerance.In the aspect of quality evaluation after cleaning,the combination of element analysis and morphology observation is adopted.The morphology of oil filters and nozzles before and after cleaning was observed by metallographic microscope,and whether cleaning was completed was preliminarily judged.Then,the surface roughness and damage of filter and nozzle were measured by laser confocal microscope.In order to study the cleaning process,the products after cleaning were collected and observed by SEM,so as to speculate the mechanism and action process of the cleaning process.It is found that laser cleaning can remove the oil and metal debris mixture on the surface of the oil filter,remove the carbon deposit layer on the surface of the nozzle,and restore the function of the oil filter and the nozzle.This technology helps to reduce maintenance costs and prolong the service life of aero-engines.