A tungsten (W)-doped microarc oxidation (MAO) coating on a TC4 titanium (Ti) alloy drill pipe was prepared by adding sodium tungstate (Na₂WO₄) into electrolytes. The effects of adding different concentrations on the electrical conductivity of the electrolyte and the performance and structure of MAO coatings on the titanium alloy drill pipe were studied. The electrical conductivity of the solution was tested using Ohm’s law. The surface morphologies of the coatings were observed by scanning electron microscopy. The element contents of the MAO coatings were analyzed by energy-dispersive spectroscopy. The hardness of the coatings was measured by using a microhardness tester. The phase composition was analyzed by X-ray diffraction, and the corrosion resistance was evaluated by polarization curves. The results show that orthotungstate (WO₄ ²⁻) begins to form tungsten trioxide (WO₃) when the temperature of the microarc discharge area is above 1314 K. With increasing sodium tungstate doping concentration, the conductivity of the solution increases first and then decreases, and the hardness and corrosion resistance of the coatings also show an identical trend. Tungsten doping slightly affects the phase composition of the MAO coating, and it is helpful in improving the hardness and corrosion resistance of the coatings. The optimum doping concentration is 3 g/l in this work.

中文翻译：

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钨掺杂对Ti6Al4V钻杆上MAO涂层性能的影响

通过添加钨酸钠（Na ₂ WO ₄）在TC4钛（Ti）合金钻杆上制备掺钨（W）的微弧氧化（MAO）涂层）变成电解质。研究了添加不同浓度对电解质电导率的影响以及钛合金钻杆上MAO涂层的性能和结构。使用欧姆定律测试溶液的电导率。通过扫描电子显微镜观察涂层的表面形态。通过能量色散光谱法分析了MAO涂层的元素含量。通过使用显微硬度测试仪测量涂层的硬度。通过X射线衍射分析相组成，并通过极化曲线评价耐腐蚀性。结果表明原钨酸盐（WO ₄ ²⁻）开始形成三氧化钨（WO ₃当电弧放电区域的温度高于1314 K时。随着钨酸钠掺杂浓度的增加，溶液的电导率先升高，然后降低，涂层的硬度和耐蚀性也呈现出相同的趋势。钨掺杂会稍微影响MAO涂层的相组成，并有助于提高涂层的硬度和耐蚀性。在这项工作中，最佳掺杂浓度为3 g / l。