磨粒环境下超高分子量聚乙烯的摩擦学行为研究

Tribological Behavior of UHMWPE in Abrasive Environment

井下装备的密封结构极易受到钻井液中颗粒的侵蚀而发生磨粒磨损最终导致密封失效,明确颗粒对密封件的损伤机理是提升密封性能延长密封寿命的关键.本研究中通过配置含二氧化硅颗粒的膨润土基液建立井下的磨粒环境,以常用于制作密封件的超高分子量聚乙烯(UHMWPE)材料作为研究对象,采用正交试验法研究颗粒浓度和尺寸对材料磨粒磨损行为的影响关系.正交试验分析结果表明:颗粒尺寸对UHMWPE摩擦学行为的影响程度显著高于颗粒浓度.在不同颗粒尺寸环境中对摩擦过程中的摩擦系数、材料磨损量和磨损形貌的变化行为展开分析时发现,摩擦副的摩擦系数和磨损量均表现出随着颗粒尺寸增加而逐渐增加的趋势,磨损状态逐渐恶化.此外,材料的表面磨损形态随颗粒尺寸的变化表现出“颗粒尺寸效应”.研究结果揭示了UHMWPE的磨粒磨损机理,为材料的工程应用和井下密封结构的设计提供了参考.

As one of the most critical and basic components of downhole drilling equipment,the seals can ensure the performance and service life of the equipment,which is an important index for evaluating the efficiency of downhole equipment.However,the complex and harsh working environment in the underground causes seals to be susceptible to abrasive wear leading to failure,which reduces the reliability of downhole equipment and drilling efficiency.As a sealing material with excellent abrasion resistance,it is necessary to study the abrasion failure mechanism of ultra-high molecular weight polyethylene(UHMWPE)in abrasive environments,which is helpful for improving sealing performance and prolonging sealing life.In order to simulate the damage and failure behavior of UHMWPE materials in fluid dynamic sealing conditions,the pin/disk friction pair composed of UHMWPE pin specimens and 304 stainless steel metal disks was studied.Orthogonal analysis was used to analyze the damage characteristics in environments with different particle concentrations and different particle sizes,and the influence of the particle environment on the tribological behavior of UHMWPE was discussed.The analytical results of orthogonal tests showed that the effect of particle size on the tribological properties of the material was stronger than that of particle concentration.Analysis of the behavior of friction coefficient and material wear in different particle concentration environments revealed that the material friction coefficient and mass loss changed less with the increase in particle concentration.The main reason for this was that the change in particle concentration did not change the wear mechanism of the material and consequently had a weak effect on its tribological properties.And the wear state of friction pairs in different sizes particle environments demonstrated a significant deterioration trend with increasing particle size.Scanning electron microscopy(SEM)analysis of the wear surface of UHMWPE showed that the surface of the material exhibited different forms of damage in the environment of different particle sizes,that was,the results of the research under different particle sizes followed the"particle size effect".Performance was as follows:small sized particles on the material wear was very slight,the material in this particle environment was mainly manifested in the pleated deformation;medium sized particles on the material in the form of damage to the ploughing,and produced plough grooves along the sliding direction on the wear surface;and the sealing material in the large sized particles environment was mainly subjected to the three-body abrasive wear,the wear surface was mainly manifested in the fibrous abrasion debris generated by the particles rolling micro-cutting.This study established the abrasive media environment for the drilling tool seals,clarified the damage behavior characteristics of UHMWPE in different concentrations and sizes of abrasive particles,revealed the failure mechanism of UHMWPE in abrasive wear,provided theoretical and technical references for the design and optimization the sealing structure in abrasive environment,and was helpful for the promotion of the application of UHMWPE materials in complex engineering environments.