Abstract Helicopter drivetrain components depend on oil lubrication to maintain elastohydrodynamic lubrication between sliding surfaces and are susceptible to a loss of lubrication event. A loss of lubrication event starves the mechanical interfaces of oil, pushing them from elastohydrodynamic toward mixed and boundary lubrication regimes. In those regimes, scuffing initiation and thermal runaway occur, resulting in a loss of torque transmission. Lubricious nanocomposite coatings made of a molybdenum disulfide and graphitic carbon are studied in combination with a titanium carbon nitride (TiCN) hard sublayer to improve scuffing resistance. Two experimental methods using a rotating ball-on-disc tribometer were conducted to evaluate the scuffing performance of the coatings. The first method is a load capacity experiment that incrementally increases load until either a maximum stress of 2.38 GPa or scuffing occurs. The second method is a loss of lubrication experiment that maintains a constant speed and contact stress with a running-in period before the lubricant supply is turned off. The elapsed time between the initiated scuff and the oil supply removal is the key experimental result. Experimental results show the time to scuffing initiation after loss of lubrication supply is extended with the application of a nanocomposite coating on a hard sublayer above the application of a hard coating alone and the uncoated medium superfinish baseline. Additional experiments were performed to study the effect of surface roughness and nanocomposite coating composition, but conclusions were limited due to a weaker adhesion strength of the TiCN sublayer applied with a lower deposition temperature to maintain steel substrate hardness.

中文翻译：

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带有和不带有硬质亚层的纳米复合表面涂层的直升机齿轮钢的耐磨性和润滑不足

摘要 直升机传动系统部件依靠油润滑来维持滑动表面之间的弹性流体动力润滑，并且容易受到润滑损失事件的影响。润滑损失事件使油的机械界面饥饿，将它们从弹性流体动力学推向混合和边界润滑状态。在这些情况下，会发生擦伤和热失控，导致扭矩传递的损失。研究了由二硫化钼和石墨碳制成的润滑纳米复合涂层与氮化碳钛 (TiCN) 硬质亚层相结合，以提高抗划伤性。进行了使用旋转球盘摩擦计的两种实验方法来评估涂层的划伤性能。第一种方法是负载能力实验，它逐渐增加负载，直到最大应力为 2.38 GPa 或出现划伤。第二种方法是失润滑试验，在润滑剂供应关闭之前，保持恒定的速度和接触应力，并有一段磨合期。启动磨损和供油去除之间经过的时间是关键的实验结果。实验结果表明，在单独施加硬涂层和未涂覆的中等超精加工基线之上，在硬子层上施加纳米复合涂层可延长在失去润滑供应后开始划伤的时间。进行了额外的实验以研究表面粗糙度和纳米复合涂层组合物的影响，