A Study On Tribological Behaviors Of Polymer-Metal Interface In Seawater

Using seawater instead of lubricating oil as lubrication medium has many advantages,on the one hand,seawater is low cost,recycling,reliable,on the other hand,water can avoid pollution which caused by leakage of lubricating oil.This makes the water to be the most promising lubricating medium.Polymers are being increasingly used in the field of tribology because of their low frictional coefficient,light weight,high strength,and erosive resistence in comparison with metal.In this paper,tribological and tribocorrosion properties of polypehenylenesulfide rein and polyetheretherketone matrix composites under water lubrication conditions have been studied.It provides an important throretical and experimental basis of polymer matrix composites in the application of hydropower,shipping marine operations and how to improve the service life and so on.The main work and conclusions are as follows:Friction and wear properties of polyphenylene sulfide composites have been investigated using a MRH-3 type wear tester.The frction pairs were ful y immersed in sea water during the whole test.The experimental results indicate that the addition of BN or SiC nanoparticles into PPS matrix enhances significantly the tribological performance at loads varying from 50 N to 200 N.In comparison to BN nanoparticles,SiC nanoparticles exert superior friction-and wear-reduction roles.When sling takes place at 50 N and 100 N,the addition of Si₃N₄ nanoparticles plays a negative role in tribological performance of PPS.On the contrary,Si₃N₄ nanoparticles greatly reduce the friction and wear at 200 N.It is inferred that when the nanoparticles were released from the polymer onto the sliding interface,their tribochemical products,i.e.SiO₂ gel,were digested within the tribofilm.It is believed that the hydrolysis products improve the load-bearing capability of the tribofilm and provides an excellent boundary lubrication effect.Tribocorrosion properties of polyetheretherketone matrix composites friction interface were investigated using an MFT-EC-4000 Pin-On-Disc tribometer.The frction pairs were fully immersed in sea water during the whole test.The experimental results indicate that h-BN nanoparticles and SCF synergistically improved the wear resistance of PEEK.When sliding took place with PEEK/SCF/h-BN,the stainless steel exhibited enhanced tribocorrosion resistance under various electrochemical conditions,in comparison to the sliding against PEEK/SCF.It was identified that H3BO3 and B₂O₃ deriving from hydrolysis reactions of h-BN were arrayed in the boundary film formed on the steel surface.Inclusion of layer-structured H₃BO₃ and B₂O₃ can enhance resilience of the surface layer against tangential stress occurring on the rubbing interface.As a consequence,a load-carrying boundary film was developed covering the steel surface,as is deemed essential for boundary lubrication of the sliding pair and for strengthening passivation of the steel.