ISSN   1004-0595

CN  62-1224/O4

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限量供油条件下表面润湿性对纯滑点接触润滑特性影响的试验研究

Effect of Surface Wettability on Lubrication Performance Under Pure Sliding Condition

  • 摘要: 限量供油条件下,利用AF (Anti-fingerprint)疏油涂层提高摩擦副表面的自集油作用,改善摩擦副在纯滑条件下的润滑特性和承载能力. 首先在润滑滚道表面或滚动体表面涂敷AF疏油涂层,利用高黏度聚异丁烯润滑油在纯滑条件下容易产生油膜凹陷的特性,使用点接触光弹流润滑油膜测量仪探究了充分及限量供油条件下不同润湿性表面对润滑油膜形态的影响. 通过对油池及膜厚形态的分析发现,在限量供油条件下,润滑滚道表面涂敷AF疏油涂层降低了表面润湿性,相较于原始表面具有更好的集油效果,减缓了乏油程度;油膜凹陷由下弦月形状转变为椭圆形状,凹陷膜厚和最小膜厚随速度增大而逐渐升高. 载荷对油膜凹陷形态影响显著,载荷越大入口油膜凹陷越明显. AF疏油涂层增强了入口处油膜的反常堆积现象,凹陷面积及膜厚表现出上升的趋势. 摩擦力测量试验表明:在充分或者限量供油条件下,原始表面和AF疏油涂层表面摩擦系数均呈现出Stribeck曲线形状. 原始表面摩擦系数随着润滑状态的优化逐渐下降,速度继续增加,充分供油产生的搅动阻力导致摩擦系数升高. 限量供油导致的乏油状态导致摩擦系数随着速度增加而迅速增加. AF表面在充分或者限量供油条件下均表现出较好的降低摩擦系数的效果,与其表面滑移特性和自集油作用有关.

     

    Abstract: In industrial lubrication practice, excessive lubricating oil is often applied to minimize wear on contact pairs and extend the lifespan of machinery. However, this approach may result in problems such as elevated oil temperature and environmental pollution. Limited lubricant supply is now receiving increased recognition. The objective of limited lubricant supply is to optimize the efficiency of lubricant utilization and guarantee optimum lubrication of interacting surfaces during operation. To achieve this, different methods have been suggested, including employing surface textures, applying chemical coatings, or integrating specific physical structures. In this study, under the condition of limited oil supply, the AF (Anti-fingerprint) oleophobic coating was used to improve the oil replenishment on the surface of the friction pair, improve the lubrication characteristics and load-bearing capacity under pure sliding condition. First, AF oleophobic coating was applied on the surface of the lubrication raceway or rolling element. By using the property of high-viscosity polyisobutylene lubricating oil to easily form oil film dimples under pure sliding conditions, a homemade optical EHL film test rig was used to investigate how different surface wettability levels affect the shape of the lubricating oil film under various oil supply conditions. The treated AF surface demonstrated oleophobic properties, with the lubricant primarily distributed on the designated lubricating track, resulting in improved lubrication performance compared to the untreated surface. By analyzing the oil pool shape and film thickness under limited oil supply, it was determined that the oleophobic coating on the lubrication track surface outperforms the rolling element surface in terms of oil replenishment effect. Additionally, the oil film dimple shape transitions from a crescent shape to an elliptical shape. The dimple film thickness and the minimum film thickness increased gradually as the speed increased. The load had a significant impact on the morphology of the oil film dimple. As the load increased, abnormal accumulation easily occurred at the inlet of the contact area. The AF oil oleophobic coating enhanced the abnormal accumulation of oil film at the inlet, leading to an increase in the dimple area and film thickness. By using AFM to observe the microstructure of the original surface and AF surface, it was found that the microstructure of AF surface showed nano convex peaks, with a higher roughness compared to the original surface. The change in surface wettability and low surface energy were key factors in reducing friction. The friction measurement experiment showed that under the condition of fully or limited oil supply, the friction coefficient of both the original surface and the AF surface followed a Stribeck curve, displaying a pattern of declining and then increasing. The frictional coefficient of the original surface decreased gradually as the lubrication state was optimized, while the stirring resistance resulting from adequate oil supply increased with speed increment. The starved lubrication state caused by limited oil supply led to a rapid increase in friction coefficient with increasing speed. Under the condition of fully or limited oil supply, the AF surface showed a better effect of reducing the frictional coefficient, which was related to the surface slippage characteristics and replenishment effect.

     

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