Friction And Wear Characteristics Of Fluorine Rubber Seals Under Abrasive Condition

With the development of "deep sea,deep ground,deep space" strategy,drilling engineering has become a hot topic.For drilling industry,the sealing problem of drilling tool is one of the main factors that affect its life and drilling efficiency.In the well,abrasive wear caused by cuttings is a common reason for sealing failure in drilling,which greatly affects the sealing ability and service life of seals,thus reducing the life of drilling equipment and reducing drilling efficiency.When the abrasive particles invade the sealing pair,it will inevitably break the abrasive particles,which will directly lead to the change of particle size and the change of the movement form of the abrasive particles,and affect the wear mechanism.In this paper,the influence of pressure and roughness on the fragmentation form and movement state of the three-body abrasive wear was studied,and the influence of the fragmentation form and movement state of the abrasive particles after invading the sealing pair on the three-body abrasive wear was analyzed.Therefore,the study of abrasive particle crushing process is of great significance for the three-body abrasive wear in the whole drilling engineering.In the first part of the paper,the friction and wear process of SiO2 particles after entering the sealing interface between the fluororubber(FKM)seal and 304 stainless steel(SS304)was studied.The effects of particle state change on the evolution of friction coefficient,wear quantity,wear morphology and wear mechanism were discussed in detail.The results show that the wear process can be divided into three stages.In addition,the main reasons for the change of the wear mechanism are the change of the motion state of the abrasive particles and the continuous crushing process.On this basis,the change rule of wear mechanism of sealing pair under abrasive wear condition was determined.The results of this study enhance our understanding of the abrasive wear degradation of rubber seals in practical drilling applications.In order to study the influence of different initial assembly pressures on the abrasive particle breakage of the downhole sealing pair,which leads to the change of three-body abrasive wear mechanism,a comparative experiment was carried out on the three-body abrasive wear of 304 stainless steel by fluorine rubber under different initial assembly pressures.The results show that the pressure affects the fracture mode and degree of the abrasive particles between the sealing interfaces.The different crushing modes of abrasive particles lead to the different wear mechanism under the two conditions.The wear mechanism under high pressure changes from three-body wear to two-body wear and finally to three-body wear.However,the wear mechanism changes from the initial two-body abrasive wear to the three-body abrasive wear and finally to the two-body stickslip wear at lower pressure.During the long time of the sealing pair working in the mine,the roughness of the metal matching pair will become rough due to the long time wear.In order to study the influence of the roughness of metal parts in the downhole sealing pair on the three-body abrasive wear,a comparative experiment was carried out on the three-body abrasive wear of 304 stainless steel by fluorine rubber under different metal pair roughness.The results show that in the early wear stage,a large area of adhesive layer is formed behind the abrasive particles,and the macroscopic appearance is "comet-like".Ploughing action of stainless steel pair on rubber ring and carrying action of abrasive debris on high roughness stainless steel surface lead to a large number of adhesive layers on rubber ring surface.In addition,the results of this study enable us to have a deeper understanding of the effect of roughness on the wear reduction of sealing pairs,which is conducive to strengthening the application of rubber and metal pairs in actual drilling engineering.