Study On Preparation Process And Properties Of Polyetheretherketone-based Composite Coatings

Wear,as the main form of energy consumption and component failure,brings huge economic losses and waste of resources to our country every year.Therefore,based on the problem of failure of precision mechanical parts during operation,a new kind of three-component polymer composite coating was proposed and applied to the surface of mechanical parts.Polyetheretherketone powder was used as the matrix material.At the same time,graphite and polytetrafluoroethylene were added to produce polyetheretherketone composite coatings with excellent performance,which effectively prevented from failure of mechanical parts during operation.In this thesis,substrate pretreatment,preparation method,formulation,preparation process and the effect of graphite content on the performance of the composite coating were studied.The specific works were as follows:?1?First,the effect of three kinds of surface pretreatment?sandblasted treatment,titanium oxide titanium nitride transition layer,and nickel-aluminum alloy transition layer?on the adhesion strength of polyetheretherketone-based composite coatings was investigated.It was found that the adhesion strength of the nickel-aluminum alloy trans ition layer has a maximum of 3000N,because the structure between nickel-aluminum alloy trans ition layer and the composite coating was interdigitated.?2?PEEK-based composite coatings were prepared by electrostatic spraying and cold-pressing sintering,respectively.The structure,mechanical properties and tribological properties of the composite coatings prepared by these two methods were explored.In the electrostatic spraying process,the powder was not completely melted,and the coating was easily mixed with air.So the coating was not closely connected with the substrate,and the porosity was high ins ide the coating.On the contrary,the coating prepared by cold-pressing sintering had excellent comprehensive performances and the density was high.The hardness,friction coefficient and the wear rate of PEEK-based composite coating prepared by cold-pressing sintering were 21.78 HV,0.0461,and 15.51×10^-6mm³?N^-1?m^-1,respectively.?3?The effect of graphite content on the structure and properties of the composite coating was studied.The results showed that the flexibility of the molecular chain decreased and movement of the chain segment reduced with the increase of the mass fraction of graphite,which resulted in the decrease of crystallinity and hardness.The friction coefficient gradually decreased,and the wear rate declined first and then increased.At the same time,the wear mechanism was dominated by abrasive wear and adhesive wear with the increase of the mass fraction of graphite.However,when the mass fraction of graphite reached to 8%,the surface of the composite coating was exfoliated,and the wear cracks were broad and deep,which indicated that at this time,the main wear mechanism changed into fatigue wear.?4?The formula of coating that made the composite coating with the best performances was studied by a two-factor comprehensive experiment.The effect of graphite mass fraction and polytetrafluoroethylene mass fraction on the performance of composite coatings were studied by using range analys is method.The results showed that:the mass fraction of graphite played an important role in improving the properties of the composite coating.A mathematical model between mass fraction of graphite X and mass fraction of polytetrafluoroethylene Y was established by regression analysis.Finally,the formula with best performance of the composite coatings was obtained by calculation:the mass fraction of graphite was 4.2%,the mass fraction of PTFE was 5.8%,and the mass fraction of PEEK was 90%.?5?The effect of pressing pressure,sintering temperature,and crystallization time on the properties of the composite coatings was studied by orthogonal experiments.The results of orthogonal experiments were analyzed by range analys is methods,and the extreme of the microhardness,friction coefficient,and wear rate were calculated.As a whole,the best performance of the PEEK-based composite coatings was acquired when the pressing pressure was 140MPa,the sintering temperature was 390°C,and the crystallization time was 70min.