A composite specimen has been employed to investigate the mechanism of coating formation on titanium by plasma electrolytic oxidation. The specimen consists of titanium/tungsten/titanium/anodic alumina/aluminium layers PEO treatment was performed under DC conditions at 20 mA cm{sup}(-2) to selected voltages in the range 15 - 450 V in alkaline pyrophosphate electrolyte. The compositions, structures and morphologies of the coatings have been examined using Rutherford backscattering spectroscopy and high resolution analytical scanning and transmission electron microscopies. Depending upon the time of treatment, two regions of coating growth were identified where layer ordering of species in the coating, with respect to that in the original specimen, was respectively conserved and altered. The latter was associated with dielectric breakdown that generated short-circuit transport paths through the coating. Thus, tungsten species were dispersed within the coating and aluminium species, originating from the aluminium layer, were transported to the coating surface.
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机译：已经采用复合样品来研究通过等离子体电解氧化钛涂层形成的机理。试样由钛/钨/钛/阳极氧化铝/铝层PEO治疗在20mA cm {sup}（ - 2）的DC条件下进行，在碱性焦磷酸电解质的范围为15-450V的选定电压下进行。使用Rutherford反向散射光谱和高分辨率分析扫描和透射电子显微镜检查涂层的组合物，结构和形态。取决于治疗时间，鉴定了两个涂层生长区域，其中涂层中物种的层排序分别保存和改变。后者与通过涂层产生短路传送路径的介电击穿相关联。因此，将钨物种分散在涂层和铝物质中，源自铝层，被输送到涂层表面。
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