Research On Formation Mechanism And Countermeasure Of Surface Defects In Dovetail Groove Broaching Of Stainless Steel Disc

Aeroengine is a important equipment in the field of national high-end equipment manufacturing and an important embodiment of a country’s industrial level.Disc is the core component of aeroengine.Its service condition is high temperature,high pressure and high speed environment,which bears great centrifugal stress.The disc is connected with the blade through the tenon groove.The tenon groove is usually formed by broaching.Its broaching surface quality has an important impact on the performance of the disc and aeroengine.The failure of most discs and blades originates from the surface defects of the tenon groove.The third stage wheel disc of a domestic aeroengine compressor is made of 14Cr12Ni2 WMo VNb electroslag stainless steel.There are surface defects in the broaching of dovetail tenon groove,and the defect formation mechanism is not clear,so it is urgent to find solutions.In this paper,the broaching process of dovetail groove is analyzed,and the forming process of dovetail groove and the design characteristics of each cutting tool are analyzed.The broaching surface defects were characterized by surface roughness instrument,ultra depth of field microscope and scanning electron microscope.It was analyzed that the main forms of defects were scale thorn and groove,and the morphology and distribution of scale thorn and groove defects were analyzed.The broaching forming process was disassembled,the cumulative broaching test of tools was carried out one by one,and the superposition effect of each tool broaching on the surface morphology was analyzed,so as to explore the formation mechanism of broaching groove and scale thorn.The chip morphology is studied,and the correlation between the chip outer surface and the machined surface characteristics is determined.Taking the tool wear as the starting point,the influence of tool wear on broaching surface quality is proved.Based on the test analysis results,the tool optimization scheme to eliminate and suppress the surface defects of scale stab and groove is put forward,and the broaching process verification test is carried out.The defects of groove and scale stab are successfully eliminated,which proves the correctness of the research.Therefore,the optimization suggestions of the whole set of tools for dovetail groove are further put forward.The main conclusions of this paper include : the amount of tooth rise has an important effect on the formation of scale spines;The surface defect prob lem is the superposition result of the action of each tool in turn,rather than the action result of a single tool.The excessive defect caused by rough broaching makes the fine broaching unable to be removed,which is the main reason for the residual broa ching defect on the wheel disc surface;Tool quality and tool defects are important factors affecting the surface quality of broaching.The damage of cutting edge and front and rear tool surfaces will directly cause broaching defects;Optimizing the cuttin g pattern,cutting allowance and tooth lift of the whole set of tools is an effective way to eliminate broaching defects and obtain high-quality surface.The research of this paper enriches the theory of broaching surface defects and provides a new idea to solve the problem of broaching surface defects.The research results have high application value for the optimization of broaching technology of domestic aero-engine disc.