电火花加工NdFeB材料的表面性能

Surface Properties of NdFeB Materials in Electrical Discharge Machining

为在NdFeB材料成型加工的同时实现其表面改性,研究了电火花加工对钕铁硼材料的影响。利用电火花成型加工技术,在不同电参数下,用紫铜电极对钕铁硼材料在绝缘介质中进行负极性加工。用扫描电子显微镜(SEM)、X射线衍射仪(XRD)等分析了材料的表面层成分、表面形貌及组织结构。通过显微硬度分析及盐雾试验,测试了材料表面硬度和耐蚀性能。结果显示:在大脉冲宽度24μs、小峰值电流5.6A下,电火花加工材料的表面质量较好。在其他参数相同的条件下,峰值电流从25.6A增大到50A,脉冲宽度从4.2μs增大到13μs时,时,硬度最大值均超过900HV0.3,比基体高出近300HV0.3。盐雾试验中加工前后材料开始出现斑点的时间差为20h,耐腐蚀性能明显发生变化。电火花加工后的钕铁硼材料表面组织中晶粒尺寸减小,并存在非晶合金相。表层非晶合金使钕铁硼材料的硬度及耐腐蚀性能得到明显地改善。

To achieve the materials forming and surface modification of NdFeB materials at the same time,the influences of NdFeB materials in electrical discharge machining（EDM）were studied.Using electrical discharge machining technology,the NdFeB materials immersed in the dielectric fluid were machined with copper electrode by reversed polarity machining under the different electrical parameters.The element,morphology and microstructure of the surface layer were studied by scanning electron microscope（SEM）and X-ray diffraction（XRD）.The changes of hardness and corrosion resistant properties were concluded by analyzing micro hardness and salt spray test.The results indicate that better surface quality of materials in EDM can be obtained by selecting the bigger pulse width of 24μs and the smaller peak current of 5.6A.When the peak current changes from 25.6to 50 Aor pulse width changes from 4.2to 13μs with other same process parameters,the maximum hardness is over 900HV0.3,about 300HV0.3higher than the substrate.The time that the spots begin to appear on the processed materials is 20 hours later than that of the substrate in the salt spray test.The grain size of surface structure is reduced and an amorphous alloy phase appears by EDM.The hardness and corrosion resistance of materials are obviously improved by the amorphous alloys.