Study On Tribological Behaviour Of Different Types Of Impregnated Phenolic Graphites For A Mechanical Seal

Mechanical seal is widely used in the process industry,marine engineering,aerospace and other fields of rotating machinery equipment shaft end seal.The seal friction pair material is usually made of impregnated graphite and hard material,which shows good sealing,reliability and wear resistance in the actual service process.Impregnated phenolic resin graphite is one of the common impregnated graphite.However,with the rapid development of the above industries,the requirements for materials are further improved.It is necessary to study the tribological behavior of impregnated phenolic resin graphite.In this paper,three kinds of impregnated phenolic resin graphite?denoted by B1,H1 and X1 codes?which are produced by three different sealing manufacturers are selected from the common graphite sealing materials in the field according to the urgent needs of the aerospace field.They are matched with pressureless sintered silicon carbide?Si C?and 25Cr3Mo A hard materials respectively.The UMT-3 friction and wear testing machine system is used to carry out dry friction and oil shortage in pin disk mode the tribological properties of graphite impregnated with phenolic resin were studied under different operating conditions.The main research contents and achievements are as follows:?1?Under the dry friction condition,with the increase of pv value,the friction coefficient of the three kinds of impregnated phenolic resin graphite and Si C decreases as a whole.With the extension of time and the increase of friction interface temperature,micron sized Si O₂particles are produced on the surface of silicon carbide disc,which leads to the decrease of friction coefficient.The reason of wear mechanism is that the slight wear and adhesive wear become more serious The friction coefficient of three kinds of graphite and 25Cr3Mo A is the same as that of Si C,but the wear rate of graphite pin is lower than that of Si C under the same condition,and the wear mechanism changes from slight abrasive wear and adhesive wear to serious adhesive wear.When H1 graphite with 45%graphitization degree is paired with silicon carbide or 25Cr3Mo A,it shows the best comprehensive tribological characteristics among the three kinds of graphite materials;in addition,the wear rate of the three kinds of graphite materials is affected by the speed more than the load.?2?Under the condition of starved-oil lubrication,the friction and wear process of three kinds of graphite and Si C or 25Cr3Mo A can be divided into four stages:stable stage,rising stage,falling stage and re stable stage.The evolution of the adjacent stage is affected by the existence time of the lubricating oil film on the friction interface and the stable formation process of the graphite transfer layer on the ground hard material surface by the graphite pin When the friction pair is in the second stage,the oil film is destroyed and the graphite layer is not formed.The existence of the mixed adhesion of graphite debris and oil on the friction interface leads to the increase of the viscosity shear force of the friction pair,which leads to the sharp rise of the temperature?3?Under the condition of oil lubrication,with the increase of pv value,the friction coefficient of the three pairs of graphite and silicon carbide basically kept below 0.1,while the friction coefficient of the pair of 25Cr3Mo A fluctuated around0.04,and the wear mechanism was adhesive wear and fatigue wear;the existence of oil film made the temperature of the friction interface drop sharply soon after the start-up,and then slow after a short time A gradual upward trend.?4?Considering the test results under different lubrication conditions,the graphite material with moderate graphitization degree has excellent comprehensive tribological properties.