油润滑状态下颗粒尺寸对PTFE/316L密封界面摩擦学行为的影响

磨粒磨损是许多流体机械中橡塑密封件常见的失效形式, 外部入侵的污染物或内部衍生的磨粒往往突破材料的耐磨强韧极限. 本文开展了聚四氟乙烯(PTFE)/316L不锈钢摩擦副在油润滑工况下的磨粒磨损实验. 评价了颗粒尺寸作用下密封副的摩擦学性能和磨损机制. 结果表明 除纯油润滑状态外, 摩擦系数与316L磨痕表面损伤程度与颗粒尺寸呈现负相关, 颗粒临界尺寸前后的颗粒运行行为和损伤机制差异显著. 在颗粒临界尺寸之上时, 完整的颗粒仅钉扎入PTFE磨痕边缘而未能穿越密封界面, 部分被碾碎的颗粒可进入接触区域中心; 随着颗粒尺寸的减小, 单个嵌入颗粒演变为堆积性“颗粒群”, 表现出明显的“砂轮效应”; 在颗粒临界尺寸之下时, 颗粒粒度小于润滑油膜厚度, 摩擦副维持流体动力润滑状态, 摩擦系数较小. 密封界面内的磨粒流不断冲蚀配副金属, 形成特殊的“PTFE-颗粒-316L”三体滚动磨损.

Effect of particle size on the tribological behavior of PTFE/316L sealing interface under oil-lubricated conditions

Abrasive wear is the main failure mode of the rubber and plastic seals in the fluid machinery. Invading contaminants and derived abrasives often break through the wear resistance and toughness limits of sealing materials. This study developed an experiment of the abrasive wear test of the PTFE cylindrical pin and 316L stainless steel disc under oil-lubricated conditions. Tribological properties and wear mechanisms of sealing pairs under the action of particle size were evaluated. The result demonstrated that the friction coefficient was negatively correlated with the wear level of 316L worn surface and particle size except for pure oil-lubricated condition. Particle running behaviour and damage mechanism below and above the particle critical size were significantly different. When the particle size was greater than critical size, only a few crushed particles could enter the centre of wear scar, with many original particles being pinned into the edge of PTFE surface instead of passing through the sealing interface. With the decrease of particle size, a single embedded particle evolved into the stacked “particle group”, and the “grinding wheel effect” from particle running behaviour had a noticeable deterioration. The particle size was smaller than the thickness of the oil film between the tribo-interface when the abrasive size was below the critical threshold. , the hydrodynamic lubrication state between the tribo-interface also held for this contacting condition, and the friction coefficient was small. Abrasive-flow invading in the sealing interface kept on eroding the metallic counterpart surface, as a result the unique “PTFE-particle-316L” three-body rolling wear was formed.