SiC添加量对建筑用7075铝合金表面微弧氧化膜性能的影响

Surface Modification of 7075 Al-Alloy with SiC-Doped Micro-Arc Oxidation Coatings

为了分析微弧氧化膜层组织性能与SiC微粉含量之间的关系,实验测试研究SiC添加量对用7075铝合金表面微弧氧化膜性能的影响。研究结果表明:当氧化时间延长,电压先迅速升高,后趋于稳定;当加入更高含量的SiC颗粒会引起电阻的增大,电压的升高,促进微弧氧化膜更快生长;当SiC加入量提高后,形成了更大的放电孔尺寸,膜层的粗糙度也显著提高;在膜层表面存在大量的烧结块,在后续膜层冷却过程中还会生成许多放电微孔。随着SiC微粉加入量由逐渐提高到4 g/L时,形成了更厚的膜层。通过分析不同氧化电压与膜层的厚度可知,加入SiC微粉能够更快实现成膜反应。发生微弧放电时,SiC颗粒已经可以发生氧化反应,引起膜层硬度的明显增大。

The surfaces of 7075 Al-alloy,an advanced oil drill-pipe material,were modified with the SiC-doped coatings synthesized by micro-arc oxidation(MAO).The influence of the SiC-doping on the microstructures,tribological properties and synthesis of MAO coating was investigated with X-ray diffraction,energy dispersive spectroscopy and scanning electron microscopy.The preliminary results show that the SiC-doping made the difference.For instance,as the SiC-content increased,the deposition-rate,thickness,surface-roughness and defect densities,including the micro-pores,pin-holes and sintered clusters,increased,because SiC-grains resulted in the increases of resistivity,MAO-voltage,number of large-sized discharge holes,followed by the formation of micro discharge-holes in cooling.Doping at a SiC-content of 4 g/L brought about stronger hardness enhancement of the thick MAO coatings,mainly comprising γ-Al2O3,α-Al2O3 and SiO2 grains,possibly because of the micro arc oxidation of SiC grains.