Journal of Materials Engineering and Performance ( IF 2.3 ) Pub Date : 2020-06-25 , DOI: 10.1007/s11665-020-04905-8 Neeraj Ahuja , Uma Batra , Kamal Kumar
Wire electrical discharge machining (Wire EDM) is a spark erosion process that modifies the surface characteristics by creating overlapped craters and oxides on the machined surface. This oxide and metamorphic layer can be advantageous for Mg alloy in terms of improved corrosion resistance and osteoblast activities. In the current work, face-centered central composite design has been used to carry out the experiments on Wire EDM to study the influence of process parameters and to generate the correlation between input parameters and performance characteristics of ZM21 Mg alloy. Performance characteristics chosen for Mg alloy machining are cutting speed, surface roughness and corrosion rate. To identify the important input parameters and a numerical model that fits the response characteristics, analysis of variance has been used. Using a scanning electron microscope (SEM), it has been found that Wire EDM resulted in overlapped craters and formation of µ-cracks on the machined surface, influenced by discharge energy developed across the electrodes. SEM and XRF (x-ray fluorescence) analysis confirm the formation of a metamorphic layer on the machined surface which leads to corrosion resistance improvement as compared to polished ZM21 Mg alloy. Under response surface methodology, desirability function was utilized to obtain the optimal solutions for multi-response characteristics which were validated experimentally and the sample machined at optimal setting shows improved surface morphology with an oxide layer having uniform nanoscale structure. Electrochemical impedance spectroscopy analysis (for 7 days) shows an increasing trend of corrosion resistance for machined samples, which supports the application of Wire EDM for Mg alloy implants.
中文翻译:
可放电降解镁合金表面特性和腐蚀速率的电火花加工实验研究与优化
线材放电加工(Wire EDM)是一种火花腐蚀工艺,通过在加工的表面上产生重叠的凹陷和氧化物来改变表面特性。就改善的耐腐蚀性和成骨活性而言,该氧化物和变质层对于Mg合金可能是有利的。在当前工作中,已经采用面心中心复合设计在Wire EDM上进行了实验,以研究工艺参数的影响并生成ZM21 Mg合金的输入参数与性能特征之间的相关性。选择用于镁合金加工的性能特征是切削速度,表面粗糙度和腐蚀速率。为了确定重要的输入参数和适合响应特征的数值模型,使用了方差分析。使用扫描电子显微镜(SEM),发现Wire EDM会导致重叠的凹坑,并在加工表面上形成µ裂纹,这受电极上产生的放电能量的影响。SEM和XRF(X射线荧光)分析证实,与抛光的ZM21 Mg合金相比,加工表面上形成了变质层,从而提高了耐蚀性。在响应面方法下,利用合意函数来获得针对多响应特性的最佳解决方案,这些解决方案已通过实验验证,并且在最佳设置下加工的样品显示出具有均匀纳米级结构的氧化物层的改善了的表面形态。电化学阻抗谱分析(连续7天)显示,机加工样品的耐蚀性呈上升趋势,