Castor oil is an environment-friendly lubricant with good biodegradability and renewable behavior. However, castor oil as a green lubricant has a few shortcomings, such as a low viscosity index and low oxidative stability due to the presence of unsaturated bonds. The temperature affects the lubrication performance of castor oil. In the present study, the lubrication performance and viscosity behavior of castor oil lubricating the friction pair of a steel ball and a nickel–titanium (NiTi) alloy disk were systematically investigated under different temperatures. The results show that the lubrication performance of castor oil is influenced by temperature due to the fact that the viscosity of castor oil varies with the temperature. The coefficient of friction (CoF) of castor oil is as super-low as 0.076 at a temperature of 40°C, but is relatively high at other temperatures. The factors affecting the lubrication performance were investigated, and a possible antifriction mechanism is proposed in this study.

中文翻译：

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高温下蓖麻油的润滑性能和粘度行为

蓖麻油是一种环保型润滑剂，具有良好的生物降解性和可再生性能。然而，作为绿色润滑剂的蓖麻油存在一些缺点，例如由于存在不饱和键而导致粘度指数低和氧化稳定性低。温度影响蓖麻油的润滑性能。在本研究中，系统研究了蓖麻油在不同温度下润滑钢球和镍钛（NiTi）合金盘摩擦副的润滑性能和粘度行为。结果表明，由于蓖麻油的粘度随温度的变化而变化，因此蓖麻油的润滑性能受温度的影响。蓖麻油的摩擦系数 (CoF) 在 40°C 的温度下低至 0.076，但在其他温度下相对较高。研究了影响润滑性能的因素，并在本研究中提出了一种可能的减摩机理。