氧化时间对Ti-6Al-4V微弧氧化膜结构与性能的影响

Effects of oxidation time on microstructure and performance of micro-arc oxidation coatings formed on Ti-6Al-4V alloy

在Na3PO4电解液中于恒流条件下对Ti6Al4V合金进行了微弧氧化处理,考察了氧化时间对微弧氧化膜表面形貌、生长速率、表面硬度和相组成的影响,并对不同氧化时间所得微弧氧化膜的摩擦学性能和耐蚀性能进行了表征。研究结果表明:随着氧化时间的延长,氧化膜表面微孔孔径逐渐增大,微孔数量逐渐减少,氧化膜生长速率逐渐减小,氧化膜的厚度逐渐增加,平均表面硬度呈先增大后减小的趋势;微弧氧化膜主要由金红石TiO2和锐钛矿TiO2相组成,随着氧化时间的延长,金红石相所占比例逐渐增大;氧化时间的长短对微弧氧化膜的摩擦系数影响不大,但对其磨损寿命有着显著影响,延长氧化时间可大大提高微弧氧化膜的磨损寿命,且随着氧化时间的延长,所得微弧氧化膜的腐蚀电位逐渐增大,腐蚀电流先减小后增大。

Ceramic coatings were fabricated on Ti-6Al-4V alloy by micro-arc oxidation(MAO) at the constant current density of 6A/dm^2 in Na_3PO_4 solution. The effects of oxidation time on the surface morphologies, growth rate, surface roughness, phase composition and surface hardness of the MAO coatings obtained were investigated. Tribological properties and corrosion properties of coatings at different oxidation times were evaluated with the pin-on-disk friction and wear tester and potentiodynamic polarization tester, respectively. The results show that, with the increasing oxidation time, the number of micro-pores and the growth rate of the MAO coatings decrease, while both the size of the micro-pores and the thickness of MAO coating increase. The average surface hardness increases at the initial stage of the oxidation process, then decreases. The MAO coating is mainly composed of rutile TiO_2 and anatase TiO_2, and the content of rutile TiO_2 increases with the increasing oxidation time. Oxidation time has little influence on the friction coefficient of the MAO coatings against GCr15 steel ball, but has much more influence on the wear life of the MAO coatings, the increase of oxidation time can improve wear life. With oxidation time increasing, the corrosion potential of the MAO coating in 3 5% NaCl(mass fraction) solution increases, but its corrosion current firstly decreases, then increases.