恒压时间对ADC12合金恒流-恒压微弧氧化膜层组织与性能的影响

Effect of Constant Pressure Time on Microstructure and Properties of Constant Current and Constant Pressure MAO Coatings on ADC12 Alloy

目的探究先恒流一定时间再恒压不同时间对ADC12高硅铝合金微弧氧化膜层组织与性能的影响,并从中选择较优的氧化时间组合。方法选择双极性脉冲电源,在先恒流(11 A/dm^(2))35 min后,再恒压(550 V)不同时间(5、15、25、35 min),制备微弧氧化陶瓷膜层。通过采用扫描电子显微镜(SEM)、金相显微镜、X射线衍射仪(XRD)、HT-600摩擦磨损试验机、电化学工作站(极化曲线、阻抗谱)等设备来表征表面形貌、膜层厚度、物相组成、磨损率以及耐腐蚀性。结果在先恒流再恒压下制备的微弧氧化膜层,其厚度随着氧化时间的延长呈现先增长后下降的趋势。先恒流35 min再恒压25 min所制备的膜层厚度最厚,为25μm;微弧氧化膜层中都存在α-Al_(2)O_(3)、Υ-Al_(2)O_(3)和Al_(2)SiO_(5)相;随着氧化时间的延长,微弧氧化膜层的磨损率出现先增长后下降的趋势。在先恒流35min再恒压5min所制备膜层的摩擦系数最小,仅为0.78。氧化时间的变化对ADC12铝合金MAO膜层耐蚀性的影响较大,腐蚀电位随着氧化时间的延长呈现先上升后下降的趋势,同时腐蚀电流的变化趋势也与腐蚀电位相同。综合考虑,在先恒流35 min再恒压25 min所制备的膜层,其耐腐蚀性较好。结论先恒流(11 A/dm^(2))35 min再恒压(550 V)25 min时所制备的微弧氧化膜层较厚,致密性较好,耐蚀性最佳。

The work aims to explore the influence of the combination of the constant current first and then plus constant voltage on the microstructure and properties of ADC12 high Si-Al alloy micro-arc oxide coating and select the optimal oxidation time combination.The MAO coatings were prepared under constant current of 11 A/dm^(2) for 35 min first and then plus constant voltage of 550 V for different oxidation time(5 min,15 min,25 min,35 min) by bipolar pulse power,and they were studied by scanning electron microscope(SEM),X-ray diffraction(XRD),HT-600 friction and wear testing machine and electrochemical work station.The results showed the thickness of the coating first increased and then decreased as the oxidation time increases under the method of first constant current and then constant voltage,and When the oxidation time was the constant current for 35 min first and then plus constant voltage for 25 min,the thickness of the coating was 25 μm.α-Al_(2)O_(3),γ-Al_(2)O_(3)and Al_(2)SiO_(5)phases existed in the MAO coating;with the increase of oxidation time,the wear rate of coating increases first and then decreases.And when the oxidation time was the constant current for 35 min first and then plus constant voltage for 5 min,the friction coefficient of the coating was the smallest,only 0.78;Different oxidation time had a significant effect on the corrosion resistance of ADC12 aluminum alloy MAO coating.The corrosion potential increases first and then decreases with the increase of oxidation time.Meanwhile,the change trend of corrosion current is the same as that of corrosion potential.Hence,when the oxidation time was the constant current of 11 A/dm;for 35 min first and then plus constant voltage of 550 V for 25 min,the coating is of thicker coating,better density and better corrosion resistance.