Bhutta Muhammad Usman, Khan Zulfiqar Ahmad, Garland Nigel
Department of Design & Engineering, NanoCorr, Energy & Modelling (NCEM) Research Group, Talbot Campus, Bournemouth University, Fern Barrow, Poole BH12 5BB, UK.
School of Mechanical & Manufacturing Engineering (SMME), Campus H-12, National University of Sciences & Technology (NUST), Islamabad 44000, Pakistan.
Materials (Basel). 2018 Dec 22;12(1):36. doi: 10.3390/ma12010036.
This article presents a wear study of Ni⁻Al₂O₃ nanocomposite coatings in comparison to uncoated steel contacts under reciprocating motion. A ball-on-flat type contact configuration has been used in this study in which a reciprocating flat steel sample has been used in a coated and uncoated state against a stationary steel ball under refrigerant lubrication. The next generation of environmentally friendly refrigerant HFE-7000 has been used itself as lubricant in this study without the influence of any external lubricant. The thermodynamic applications and performance of HFE-7000 is being studied worldwide, as it is replacing the previous generation of refrigerants. No work however has been previously performed to evaluate the wear performance of HFE-7000 using nanocomposite coatings. The wear scar developed on each of the flat and ball samples was studied using a Scanning Electron Microscope (SEM). The micrographs show that a combination of adhesive and abrasive wear occurs when using uncoated steel samples. Micro-delamination is observed in the case of Ni⁻Al₂O₃ nanocomposite coatings accompanied by adhesive and abrasive wear. Wear volume of the wear track was calculated using a White Light Interferometer. Energy-Dispersive X-ray Spectroscopic (EDS) analysis of the samples reveals fluorine and oxygen on the rubbing parts when tested using coated as well as uncoated samples. The formation of these fluorinated and oxygenated tribo-films helps to reduce wear and their formation is accelerated by increasing the refrigerant temperature. Ni⁻Al₂O₃ nanocomposite coatings show good wear performance at low and high loads in comparison to uncoated contacts. At intermediate loads the coated contacts resulted in increased wear, especially at low loads. This increase in wear is associated with the delamination of the coating and the slow formation of protective surface films under these testing conditions.
本文介绍了Ni⁻Al₂O₃纳米复合涂层在往复运动下与未涂层钢接触的磨损研究。本研究采用了球-平面型接触配置，其中一个往复运动的平面钢样品在有涂层和无涂层状态下，在制冷剂润滑下与一个固定的钢球接触。本研究中使用了新一代环保制冷剂HFE-7000作为润滑剂，不受任何外部润滑剂的影响。由于HFE-7000正在取代上一代制冷剂，其热力学应用和性能正在全球范围内进行研究。然而，以前尚未进行过使用纳米复合涂层评估HFE-7000磨损性能的工作。使用扫描电子显微镜（SEM）研究了每个平面和球样品上形成的磨损痕迹。显微照片显示，使用未涂层钢样品时会发生粘着磨损和磨粒磨损的组合。在Ni⁻Al₂O₃纳米复合涂层的情况下观察到微分层，同时伴有粘着磨损和磨粒磨损。使用白光干涉仪计算磨损轨迹的磨损体积。对样品的能量色散X射线光谱（EDS）分析表明，在使用有涂层和无涂层样品进行测试时，摩擦部件上存在氟和氧。这些氟化和氧化摩擦膜的形成有助于减少磨损，并且通过提高制冷剂温度可加速其形成。与未涂层接触相比，Ni⁻Al₂O₃纳米复合涂层在低负荷和高负荷下表现出良好的磨损性能。在中等负荷下，有涂层的接触导致磨损增加，尤其是在低负荷下。这种磨损的增加与涂层的分层以及在这些测试条件下保护表面膜的缓慢形成有关。
