HVOF喷涂AlCoCrFeNi高熵合金涂层在模拟海水钻井液中的腐蚀和磨损性能研究

目的 提高钻具关键易损零部件在海洋钻探实际应用中的耐腐蚀和磨损性能。方法 采用超音速火焰喷涂技术（HVOF）制备Al CoCrFeNi高熵合金涂层。使用电化学工作站对涂层和35CrMo钢基体（常用的钻具材料）进行电化学测试，电化学测试包括动电位极化曲线测试和电化学阻抗谱（EIS）测试。采用摩擦磨损试验机对涂层在模拟海水钻井液中不同载荷和不同滑动速度下的磨损行为进行研究。采用扫描电子显微镜及X射线能谱仪对磨痕表面微观形貌及成分进行分析，利用三维白光干涉形貌仪测量涂层的磨痕三维形貌及磨损体积。结果 HVOF喷涂Al Co Cr Fe Ni高熵合金涂层在模拟海水钻井液中的耐腐蚀性优于35CrMo钢基体，可以起到有效的腐蚀防护作用。相同条件下，Al CoCrFeNi高熵合金涂层的耐磨性优于35CrMo钢基体。在滑动摩擦磨损过程中，随着载荷及滑动速度的增大，涂层的平均摩擦系数和磨损率均增大，且涂层的磨粒磨损程度加重。当载荷为6 N时，涂层发生疲劳磨损；当滑动速度为0.15 m/s时，涂层出现粘着磨损。模拟海水钻井液对涂层磨损性能的影响可以分为2个方面。一方面可以起到润滑作用，模拟海水钻井液显著改...

Corrosion and Wear properties of HVOF Sprayed AlCoCrFeNi HEA Coating in Simulated Seawater Drilling Fluid

With the depletion of land resources, the development of marine resources (such as oil, natural gas hydrate, solid minerals, etc.) has become one of the important strategic measures in China. The development of marine resources is inseparable from advanced marine drilling equipment. In order to ensure the reliability of offshore drilling, drilling equipment is put forward higher requirements for material properties, especially surface properties. However, only improving the performance of the substrate itself cannot meet the service requirements of the equipment in harsh conditions. Therefore, it is an effective method to use advanced surface engineering technology to strengthen the key vulnerable parts such as the drill pipe, casing and operation pump of offshore drilling equipment. The AlCoCrFeNi High-Entropy Alloy (HEA) is an excellent wear and corrosion resistant material. At present, there are many researches on the corrosion and wear properties of AlCoCrFeNi HEA, but there are few researches on the wear of AlCoCrFeNi HEA coating in drilling fluid, especially the tribological properties of AlCoCrFeNi HEA coating in seawater drilling fluid. In this paper, in order to improve the corrosion resistance and wear resistance of key wearing parts of drilling tools in practical application of offshore drilling, the AlCoCrFeNi HEA coating was prepared by High Velocity Oxygen Fuel (HVOF) technology, which was intended to be applied to the surface protection of offshore drilling equipment. The coating and 35CrMo steel substrate were subjected to electrochemical tests using electrochemical tests, including potentiodynamic polarization curve measurements and electrochemical impedance spectroscopy (EIS) measurements. The sliding wear behavior and failure mechanism of AlCoCrFeNi HEA coating sprayed by HVOF in simulated seawater drilling fluid were studied by friction and wear testing machine under different loads and sliding speeds. The wear surface and composition of the coating were analyzed by scanning electron microscope (SEM) and X-ray energy dispersive spectrometer (XRD). The wear three-dimensional morphologies and wear volumes of the coating were measured by three-dimensional white light interferometry. The results show that the corrosion resistance of AlCoCrFeNi HEA coating is better than 35CrMo steel substrate in the simulated seawater drilling fluid, indicating that AlCoCrFeNi HEA coating can play an effective role in the protection of offshore drilling tools. Under the same conditions, the wear resistance of AlCoCrFeNi HEA coating is better than that of 35CrMo steel substrate. The average COF and wear rate of AlCoCrFeNi HEA coating increase with the increase of load and sliding speed in the process of sliding friction and wear and both the average coefficient of friction and wear rate of the coating increase. With the increase of load and sliding speed, the abrasive wear degree of the coating increases, and the fatigue wear of the coating occurs when the load is 6 N. When the sliding speed is 0.15 m/s, the coating appears adhesive wear. In addition, the influence of simulated seawater drilling fluid on the wear performance of the coating can be divided into two aspects:on the one hand, it can play the role of lubrication. Simulated seawater drilling fluid significantly improves the friction and wear properties of the coating, and reduces the average friction coefficient and wear rate of the coating. On the other hand, the coating has been corroded to form corrosion pits, which will aggravate the wear of the coating. Above all, the HVOF sprayed AlCoCrFeNi HEA coating has excellent corrosion resistance in simulated seawater drilling fluid,which can effectively reduce wear, and is expected to be applied to the surface protection of key parts of offshore drilling tools.