| Copper metal generally has good thermal conductivity and is a commonly used electrode material for electric discharge machining（EDM）（brass,copper tungsten,copper,etc.）.However,copper metal exhibits a sharp decline in corrosion resistance in harsh environments such as high temperatures and salt spray,resulting in behaviors such as electrical corrosion,wear corrosion,and galvanic corrosion;and when copper metal is used as an electrode material for EDM processing,the electrode is affected by the high temperature flow field and will generate higher electrode loss.This paper proposes a method for preparing particle doped Micro-arc oxidation（MAO）composite film on the surface of brass to address the inherent surface corrosion problem of copper metal,and the high temperature loss that occurs when it is used as an EDM electrode to process workpieces.The main research content of this article is as follows:（1）Firstly,in response to the difficulty in forming a stable plasma discharge channel during the initial stage of Micro-arc Oxidation on the surface of brass,a mixed electrolyte composed of Na2Si O3 and Na OH was prepared.The electrical parameters of MAO were optimized through orthogonal tests and range analysis.The optimization results were as follows:Oxidation time of80 minutes,Duty cycle of 20%,Forward voltage of 550V,and Reverse voltage of 5V;after doping with Ce O2 nanoparticles,the porosity and surface roughness of the film decreased from35.11%and 3.883μm to 32.98%and 3.331μm respectively.The density and flatness of the film have been improved;the corrosion potential Ecorr and self corrosion current density icorr of the composite film are-0.0436V and 7.402×10-5A/cm2 respectively.Compared with the brass substrate and the film before particle addition,the potential increased by 60.15%and 55.1%respectively,while the self corrosion current density decreased by 3 and 1 order of magnitude.（2）Secondly,a single factor test was conducted on the concentration of Ce O2 particles:different concentrations of Ce O2 nanoparticles（0,2,4,6,8g/L）were added to the silicate electrolyte,and the MAO composite films was prepared by Micro-arc Oxidation on the brass substrate.The electrical parameters were set based on the optimal parameter combination obtained from the previous orthogonal test.The porosity and corrosion resistance of five groups of MAO composite films were characterized,the results are as follows:as the doping Ce O2concentration increased from 0 to 8g/L,the porosity of the film decreased from 36.08%to33.42%,29.02%,27.08%,and 25.36%respectively;when the Ce O2 concentration is 4g/L,the film has the maximum self corrosion potential of 0.177V and the minimum self corrosion current density of 5.589×10-5A/cm2,the film has the strongest corrosion resistance.（3）Finally,conduct a test on the machining of 304 stainless steel with brass electrodes by electric discharge machining.The EDM electrical parameters were optimized through orthogonal tests and grey correlation analysis,and the optimization results showed that the Peak current,Pulse width,Pulse interval,and Gap voltage were 3A,30μs,4μs and 50V respectively.Based on the optimal combination of EDM parameters,304 stainless steel workpieces were processed using brass electrode,MAO film electrode and MAO composite film electrode respectively.The Material removal rate（MRR）,Tool wear rate（TWR）and Surface roughness（SR）of the workpiece were compared and analyzed for the three types of electrodes.The EDM processing results show that the MRR of the three electrodes are 0.1008,0.1684,and 0.1893mg/s respectively;the TWR are 0.0366,0.0248,and 0.0205mg/s respectively;the SR of the workpieces is 3.084,2.058,and 1.873μm respectively.Compared with brass electrode,the MRR of MAO film electrode and MAO composite film electrode increased by 59.13%and 87.8%respectively;the TWR decreased by 32.3%and 43.97%respectively;the SR decreased by 33.27%and 39.27%respectively. |
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