The incorporation of particles suspended in the electrolyte into plasma electrolytic oxidation coatings on Ti and Al substrates
The incorporation of particles suspended in the electrolyte into plasma electrolytic oxidation coatings on Ti and Al substrates
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DOI：
10.1016/j.surfcoat.2020.125354
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发表时间：
2020-03-15
影响因子：
5.4
通讯作者：
Clyne, T. W.
中科院分区：
文献类型：
--
作者：
O'Hara, M.;Troughton, S. C.;Clyne, T. W.
这项研究涉及的机制，通过（细）颗粒成为纳入等离子体电解氧化（PEO）涂层时，添加到电解质。使用了三种不同类型的颗粒，覆盖了广泛的尺寸范围，并在Al和Ti衬底上进行了加工。对于其中一些组合，颗粒在化学上与预期的PEO产品相似，而对于其他组合则不同。电源为50hz交流电，具有预先选定的电流密度。已经确定的是，在化学上有利于这种反应的地方，一定会发生与颗粒达到非常高的温度有关的相变。从这一证据和其他证据可以得出结论，所涉及的主要结合机制是（细）颗粒被扫进与主动放电部位相关的孔隙，而在等离子体坍塌后，这些孔隙立即被电解质重新填充。然后，它们很可能被困住，并且在许多情况下，在下一个放电周期中，等离子体被产生时，它们会被强烈加热。典型的孔隙大小是这样的，大小在10 μ m以上的颗粒（或颗粒团）不太可能进入其中。虽然直径几微米的颗粒可以被合并，但亚微米颗粒更容易被合并。我们还得出结论，电泳力不太可能在掺入过程中发挥任何重要作用。
This investigation concerns the mechanisms by which (fine) particles become incorporated into plasma electrolytic oxidation (PEO) coatings when added to the electrolyte. Three different types of particle have been used, covering a wide size range, and processing has been carried out with both Al and Ti substrates. For some of these combinations, the particulate was chemically similar to the expected PEO product, while for others it was different. The power supply was 50 Hz AC, with a pre-selected current density. It has been established that, where such reactions are chemically favoured, phase changes can occur that must have involved the particulate reaching very high temperatures. From this and other evidence, it is concluded that the main incorporation mechanism involved is that of (fine) particulate being swept into the pores associated with active discharge sites, while they are being refilled with electrolyte immediately after collapse of the plasma. They are then likely to become entrapped, and in many cases to be strongly heated as the plasma is created during the next discharge cycle. Typical pore sizes are such that particles (or particulate clusters) above about 10 mu m in size would be unlikely to enter them. While particles a few microns in diameter can become incorporated, it takes place more readily with sub-micron particles. It is also concluded that electrophoretic forces are unlikely to play any significant role in the incorporation process.