Microstructural, corrosion and mechanical behavior of two-step plasma electrolyte oxidation ceramic coatings

两步等离子体电解氧化陶瓷涂层的结构、腐蚀和力学行为（英文）

Plasma electrolytic oxidation(PEO)is considered as a cost effective and environmentally friendly surface treatmentprocess for improving surface properties of light alloys.The formation of ceramic coatings on Ti6Al4V alloy was reported bytwo-step PEO process and its structural,electrochemical and mechanical properties with the coated samples were compared byone-step PEO process in an alkaline electrolyte.The structural properties were studied using field-emission scanning microscope(FESEM)and X-ray diffraction(XRD).Electrochemical studies were carried out using linear polarization method and in additionmechanical behaviors were investigated by means of Knoop microhardness and nanoindentation method.Results showed that thesecond step process resulted in an increase of both porosity percentage and average pore diameter on the surface.The two-stepprocess resulted in a small increase of thickness from about12.5to13.0μm.Electrochemical test results showed that applying thesecond step resulted in the decrease of both polarization resistance from1800.2to412.5kΩ/cm2and protection efficiency from97.8%to90.5%.Finally,the nanoindentation results indicated that the PEO coatings became softer but more ductile after applyingthe second processing step in acidic electrolyte.

等离子体电解氧化(PEO)被认为是提高轻合金表面性能的一种低成本和环境友好的表面处理工艺。采用两步PEO法研究Ti6Al14V合金上陶瓷涂层的形成,并将该涂层样品的结构、电化学和力学性能与在碱性电解液中采用一步PEO法的样品进行比较。利用场发射扫描电镜(FESEM)和X射线衍射(XRD)技术对其结构性能进行表征。采用线性极化法进行电化学研究,并使用Knoop显微硬度和纳米压痕法研究其力学性能。结果表明,第二步电解氧化使涂层表面孔隙率和平均孔径都增大,两步法导致涂层厚度从12.5增加到13.0μm。电化学测试结果表明,第二步导致极化电阻从1800.2下降到412.5 k?/cm^2,保护效率从97.8%降至90.5%。纳米压痕结果表明,在酸性电解液中采用第二步加工工艺后,PEO涂层变得更加柔软,但韧性更大。