Experimental Study On Abrasive Erosion And Electric Discharge Combined Machining Of EB-PVD Coated Parts

EB-PVD thermal barrier coating is widely used in aeroengine turbine blades due to its excellent properties such as high thermal insulation,low thermal conductivity,high melting point and wear resistance.It works synergistically with air film holes and plays a very important role in improving the temperature bearing capacity of hot-end parts.However,the difficult problem is how to perform microscale air film hole processing on thermal barrier coating metal components.This paper carried out an experimental study on the combination of abrasive erosion and electrical discharge machining of EBPVD coated parts.The abrasive erosion processing was first performed on the thermal barrier coating,and then the Electric spark piercing processing is performed at the position of the erosion hole,which is to explore the air film hole processing method of coating first and then making holes.Firstly,a simulation study of the abrasive erosion mechanism of EB-PVD thermal barrier coatings was carried out.Based on numerical simulation and combined with existing research results,a preliminary analysis of the material removal mechanism of the EB-PVD thermal barrier coating after abrasive grain erosion processing is performed.The results show that when a single abrasive particle impacts,the surface of the thermal barrier coating will first indent,and at the same time,the internal stress generated after the impact of the coating will propagate in the columnar crystals,and then cracks will initiate at the resulting bend.With the continuous impact of the abrasive particles and the continuous propagation and accumulation of energy,the crack will gradually expand in the bending direction of the turning belt,eventually leading to the exfoliation of the sheet,and the larger abrasive particle size and higher impact speed will increase.Destructive ability to thermal barrier coatings.Secondly,the orthogonal design of abrasive erosion of 30 ° oblique hole and 90 ° straight hole was designed to analyze the influence of abrasive concentration,jet target distance and punching time on the characteristics of hole pattern.The results show that the jet target distance is the main factor affecting the hole diameter,and the punching time is the main factor that affects the hole depth.On this basis,the BP neural network was used to predict the target distance and punching time of the desired hole pattern.The verification experiment showed that the maximum error percentage between the test result and the predicted result was not more than 6%,and a GUI interface was designed to achieve Ergonomics,ready for subsequent EDM.Finally,on the basis of the etched hole processing of EB-PVD coated parts and the single-pulse EDM temperature field simulation,the selection of EDM parameters and the experimental study of EDM at the erosion hole position were carried out.The effects of processing parameters on the erosion straight holes and the erosion oblique holes of the thermal barrier coatings were explored.Excessive peak current and pulse width will have a great damaging effect on the coating,and it will also increase the possibility that the electro-corrosion products cannot be thrown out in time and cause accumulation.