Research On The Tribocorrosion Characteristics Of Water-lubricated Friction Pairs Under Large Depth Condictions

The ocean contains abundant resources,and the development of ocean resources requires modern underwater equipment.The seawater hydraulic technology directly uses natural seawater as the working medium.It has an environmentally friendly and simple system composition and has been successfully used in underwater equipment.However,seawater is low in viscosity,contains suspended sand,and is highly corrosive,making it difficult to form a lubricating film between the friction pairs of the water hydraulic system.Friction pairs are susceptible to different degrees of friction and corrosion failure,which in turn affects the working performance and service life of underwater equipment.Secondly,the tribocorrosion characteristics of the friction pair under high hydrostatic pressure may be different from that under normal pressure.In addition,it is difficult to carry out tribocorrosion tests under high pressure.At present,there is almost no research on this aspect at home and abroad,which leads to the lack of theoretical basis for the design of friction pairs in water hydraulic systems.Based on the above problems,this paper carried out the research on the tribocorrosion characteristics of the water-lubricated friction pair under the condition of large depths.The specific research content and results are as follows:(1)The method of accurately transmitting and measuring the loading force of the tribocorrosion test rig under high pressure is studied.The gap seal and the special structure of the oil cylinder reduce the influence of additional torque on the measurement of friction torque of the test piece.The developed test rig can stably simulate the hydrostatic pressure of 80 MPa.The data acquisition and control system of the test rig was developed to collect four analog signals and control the motor speed.Four all-solid reference electrodes have been developed for corrosion research under high pressure.Tests have shown that high-purity zinc electrodes,hot-dip coated Ag/Ag Cl electrodes and silver-plated Ag Cl electrodes can all be used in a high-pressure environment of 80 MPa.(2)The effect of 0-80 MPa hydrostatic pressure on the tribological properties of polyetheretherketone was studied,and 431SS was used as a matching pair.The results show that the average friction coefficient of the pair decreases with the increase of hydrostatic pressure.The hydrostatic pressure helps reduce the wear rate of the pair.As the pressure increases,the wear mechanism of CF/PEEK changes from adhesive wear to fatigue wear,while the wear mechanism of 431SS is abrasive wear.Compared with the sliding surface after the normal pressure test,the CF/PEEK surface roughness after the high pressure test is smaller.In addition,XRD analysis showed that the crystallinity of CF/PEEK decreased linearly with hydrostatic pressure.(3)The effect of 0-80 MPa hydrostatic pressure on the tribocorrosion characteristics of WC-10Co-4Cr sliding against Si₃N₄ was studied.The results show that hydrostatic pressure has no obvious effect on its friction characteristics.The friction pair has a small friction coefficient and wear rate under different pressures,which may be related to the formation of a lubricating reaction film.Electrochemical tests show that the corrosion rate of WC-10Co-4Cr increases with pressure,and friction can accelerate the corrosion of WC-10Co-4Cr.The wear mechanism of WC-10Co-4Cr is that the corrosion of the Co Cr binder phase leads to the frictional shedding of WC particles and part of the abrasive wear;while the wear mechanism of Si₃N₄ is the peeling of the surface material caused by fatigue wear.The studied CF/PEEK,WC-10Co-4Cr and Si₃N₄ tribopairs all show excellent characteristics of low resistance,wear resistance and compression resistance in the 0-80 MPa environment.The research results have laid the foundation for the research of friction pairs under conditions of large depths.At present,both friction pairs have been successfully applied to the variable buoyancy seawater pump of the"Struggle"10,000-meter manned submersible.