Hou Fengyan, Gorthy Rukmini, Mardon Ian, Tang Da, Goode Chris
Cirrus Materials Science Ltd., 5B Target Ct., Auckland, 0627, New Zealand.
Department of Chemical and Materials Engineering, The University of Auckland, 20 Symonds Street, Auckland, 1010, New Zealand.
Sci Rep. 2022 Apr 11;12(1):6037. doi: 10.1038/s41598-022-09693-w.
Plasma electrolytic oxidation (PEO) is a surface-treatment process extensively used to protect the surfaces of light metals such as Mg, Al, and Ti. Here, we report an environmentally friendly PEO process that uses nitrogen-containing electrolytes and low voltages (120 V) to form ~ 12 micron thick, uniform, adherent and porous oxide coatings on T1 titanium alloy surfaces. We evaluated the influence of nitrogenation by comparing the coatings to alloys treated in PEO baths without nitrogen-containing compounds. Both sets of samples exhibited basalt-like morphologies with distinct variation in the pore structures. The composition analyses showed that the coatings were primarily composites of titanium oxides and silicates. The T1 Ti alloys treated with nitrogen-containing electrolytes also contained TiC and TiN. This is the first ever report of producing TiO, Ti-Si-O, TiC, and TiN composite coatings using a single PEO bath without carbide/nitride nanoparticles. The bandgaps of the coatings suggested visible light functionality. The use of nitrogen-based compounds in the PEO baths improved the hardness of the oxide layers but introduced stress-induced cracking which are potentially responsible for the reduction in corrosion resistance of the nitride and carbide containing coatings.
等离子体电解氧化（PEO）是一种广泛用于保护镁、铝和钛等轻金属表面的表面处理工艺。在此，我们报道了一种环境友好型的PEO工艺，该工艺使用含氮电解质和低电压（120V）在T1钛合金表面形成约12微米厚、均匀、附着且多孔的氧化物涂层。通过将涂层与在不含含氮化合物的PEO镀液中处理的合金进行比较，我们评估了氮化的影响。两组样品均呈现出类似玄武岩的形态，孔隙结构有明显差异。成分分析表明，涂层主要是钛氧化物和硅酸盐的复合材料。用含氮电解质处理的T1钛合金还含有TiC和TiN。这是首次报道使用单一PEO镀液在不添加碳化物/氮化物纳米颗粒的情况下制备TiO、Ti-Si-O、TiC和TiN复合涂层。涂层的带隙表明其具有可见光功能。在PEO镀液中使用氮基化合物提高了氧化层的硬度，但引入了应力诱导裂纹，这可能是含氮化物和碳化物涂层耐腐蚀性降低的原因。
