Evaluation of Temperature-Dependent Boundary Lubrication Behavior of Stearic Acid Using a Force-Controlled Tribometer,Langmuir

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Evaluation of Temperature-Dependent Boundary Lubrication Behavior of Stearic Acid Using a Force-Controlled Tribometer
Langmuir ( IF 3.7 ) Pub Date : 2024-03-26 , DOI: 10.1021/acs.langmuir.3c03846
Adarsh Divakaran ₁ , Vikas K Singh ₁ , Shubha H Nataraj ₁ , Satish V Kailas ₁

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A quick evaluation of the effectiveness of additives is important in lubricant formulation. In this study, we employed a friction-force measurement approach using a newly designed lateral force-controlled tribometer. This tribometer evaluates the lubricant properties under boundary lubrication. In this lateral force-controlled tribometer, the absence of a stiffness-altering sensor enables the modeling of the actual contact conditions without altering the contact stiffness. Indirect friction force measurement ensures precise measurements of friction properties while avoiding common measurement errors encountered in conventional tribometers, such as sensor misalignment and changes in the stiffness of the machine due to the sensor. The tribometer designed and built consists of a pendulum that measures the rate of dissipation of the oscillation amplitude as a function of time. The unique characteristics of the machine are the possibility of changing the energy input into the tribosystem without altering the tribo-contact conditions and the capability to do experiments at higher temperatures. To evaluate the capabilities of this tribometer, the impact of temperature on the frictional properties of a base oil and a blend of base oil and stearic acid (SA) (a prominent Organic Friction Modifier) is investigated. The test result shows that frictional energy dissipation decreases when stearic acid is present in the lubricant. And, as the temperature of the oil increases, the energy dissipation increases for pure base oil but reduces for the blend. The observed frictional trends are attributed to the decrease in the viscosity of the base oil with an increase in the temperature. The decrease in friction for the SA blend is attributed to tribofilm formation. Fourier transform infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS) analyses confirm the presence of the SA tribofilm on the surface. XPS indicates an increase in tribofilm quantity with rising temperatures. The kinetics of film formation and thickness increase with temperature, consequently reducing the friction in the SA blend.

中文翻译：

使用力控制摩擦磨损试验机评估硬脂酸的温度依赖性边界润滑行为

快速评估添加剂的有效性对于润滑油配方非常重要。在这项研究中，我们采用了一种摩擦力测量方法，使用新设计的横向力控制摩擦计。该摩擦磨损试验机评估边界润滑下的润滑剂性能。在这种横向力控制的摩擦测试仪中，由于没有改变刚度的传感器，因此可以在不改变接触刚度的情况下对实际接触条件进行建模。间接摩擦力测量可确保精确测量摩擦特性，同时避免传统摩擦计中常见的测量误差，例如传感器未对准以及传感器导致的机器刚度变化。设计和制造的摩擦计由一个摆锤组成，用于测量振荡幅度随时间变化的耗散率。该机器的独特特性是可以在不改变摩擦接触条件的情况下改变摩擦系统的能量输入，并且能够在更高的温度下进行实验。为了评估该摩擦磨损试验机的性能，研究了温度对基础油以及基础油和硬脂酸 (SA)（一种著名的有机摩擦改进剂）混合物的摩擦性能的影响。测试结果表明，当润滑剂中存在硬脂酸时，摩擦能量耗散降低。而且，随着油温的升高，纯基础油的能量耗散增加，但混合物的能量耗散减少。观察到的摩擦趋势归因于基础油的粘度随着温度的升高而降低。 SA 共混物摩擦力的降低归因于摩擦膜的形成。傅里叶变换红外 (FTIR) 和 X 射线光电子能谱 (XPS) 分析证实表面存在 SA 摩擦膜。 XPS 表明摩擦膜数量随温度升高而增加。成膜动力学和厚度随着温度的增加而增加，从而减少 SA 共混物中的摩擦。

更新日期：2024-03-26

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