面向钛合金微细铣削的等离子体电解氧化膜层的制备与性能分析

Preparation and Performance Analysis of Plasma Electrolytic Oxidation Coating for Micro Milling of Titanium Alloy

目的降低TC4钛合金微小零件的铣削难度,提高表面加工质量和加工效率。方法采用以NaAlO_(2)为主要成分的电解液,借助等离子体电解氧化(Plasma Electrolysis Oxidation,PEO)作用,在TC4钛合金表面原位生长厚度约为20μm的疏松多孔氧化膜层。分别使用扫描电子显微镜、X射线能谱仪对氧化膜层的结构和组成进行表征,采用测力仪、白光干涉仪对氧化膜层微细铣削时的切削力和表面粗糙度进行测量。结果氧化膜层为TC4钛合金原位生长所得,厚度较为均匀,约为20μm。结构疏松多孔,孔隙率高,孔洞分布较为均匀,与基体结合力差。与TC4钛合金相比,氧化膜层的弹性模量和硬度分别降低了79.8%和75.0%;相同切削参数下,三向铣削力分别降低了91.90%、78.13%和42.62%,表面粗糙度Ra值减小了52.6%。结论该氧化膜层较传统膜层而言,有更加疏松多孔的结构,强度更低,可明显降低微细铣削的三向力,加工表面粗糙度明显降低,且无明显的顶部毛刺。该方法显著降低了TC4钛合金微细铣削的加工难度,有效改善了加工表面质量,验证了等离子体电解氧化的方法用于辅助铣削TC4钛合金的可行性。

The work aims to reduce the milling difficulty of micro parts with TC4 titanium alloy,and improve the surface machining quality and efficiency of TC4 parts.The electrolyte with NaAlO_(2) as the main component was designed,and a porous plasma electrolytic oxidation(PEO)coating with thickness of about 20μm was grown on the surface of TC4 titanium alloy in situ by means of electrolytic plasma oxidation.The structure and composition of the PEO coating were characterized by scanning electron microscope(SEM)and energy dispersive spectrum(EDS).Meanwhile,the cutting force and surface roughness of the PEO coating during micro milling were measured by force measuring instrument and white light interferometer respectively.The results showed that the PEO coating is obtained by in-situ growth of TC4 titanium alloy,and its thickness is about 20μm.Furthermore,the structure of PEO coating is loose and porous,the porosity is higher,the distribution of pores is uniform,and the binding force with the matrix is poor.Compared with TC4 titanium alloy,the elastic modulus and hardness of PEO coating were reduced by 79.8%and 75.0%,respectively.Under the same cutting parameters,the three-dimensional milling forces were decreased by 91.90%,78.13%and 42.62%,respectively,the surface roughness Ra was reduced by 52.6%.Consequently,compared with the traditional film,the PEO coating fabricated by electrolytic plasma has a more porous structure and lower strength,which can significantly reduce the three-dimensional force of micro milling,and improve the surface roughness without top burr.This method significantly reduces the machining difficulty of micro milling for TC4 titanium alloy,improves the machining surface quality effectively,and verifies the feasibility of the plasma electrolytic oxidation method used in the auxiliary milling of TC4 titanium alloy.