Research On Ultrasonic-Electrochemical Grinding Of Small Holes In SLM-ed Superalloy

In recent years,selective laser melting(SLM)technology has gradually become the important research focus of additive manufacturing technology,but its printed parts often have insufficient mechanical properties.In order to solve this problem,this thesis studies the solid solution heat treatment and various properties of SLM-ed parts.In addition,the surface quality of the formed parts printed by SLM is usually poor,therefore,this thesis adopts the method of "SLM+ECM",it's a combination of additice manufacturing and "reduced material manufacturing".Specifically,the pre-hole is obtained by the inner jet electrochemical machining on SLM-ed plate,and then,the hole is enlarged by the ultrasonic assisted electrochemical grinding(UAECG)technology,so as to obtain the small hole with good machining accuracy and surface quality finally.The specific research contents are as follows:In this thesis,the SLM printing process of Hastelloy X nickel base superalloy was studied.The best SLM printing parameters were determined by Vickers hardness test and relative density test,which were used as the process parameters of SLM-ed workpiece in subsequent experiments.Then on this basis,the orthogonal experiment of L9(34)heat treatment-room temperature uniaxial tension was designed,and the best combination of solution treatment parameters was obtained,which was finally used as the heat treatment process parameters of the small hole machning workpiece in the following thesis.In this thesis,the electrochemical properties of SLM-ed superalloy workpiece were analyzed by linear potential sweep voltammetry test and AC impedance spectroscopy test,including the passivation and electrochemical dissolution characteristics of SLM-ed superalloy.In the aspect of numerical simulation,the electric field finite element analysis of small hole machining by UAECG is carried out,and the equivalent constant voltage method is innovatively applied to the electric field analysis of high frequency pulse electrochemical machining under the primary current distribution.At the same time,the numerical simulation analysis of electrochemical machining in hole-enlarging is also carried out,and the results of machining simulation using hemispherical-head and spherical-head grinding electrodes are compared,which provides the reference for the design of grinding electrode.In addition,the gap flow field distribution of hole-enlarging by UAECG with ultrasonic cavitation is also studied.In this thesis,the experimental study of inner jet electrochemical machining and ultrasonic assisted electrochemical grinding were carried out on SLM-ed plate.Also,we designed and prepared the ultra-thin Parylene insulating film and hemispherical-head diamond grinding electrode,studied the effects of peak-peak voltage,duty cycle and ultrasonic on small hole machining using UAECG.Finally,a small hole with a diameter of 1210?m,a repeat machining accuracy of±5?m and a surface roughness of Ra0.49?m was obtained.