Study On Flame Sprayed Carbon Nanotube Reinforced Polyetheretherketone Composite Coating

Polymer coatings are increasingly being applied to metal substrates to protect surfaces from corrosion and excessive wear.Polyetheretherketone?PEEK?has become one of the most attractive polymer materials due to its excellent thermal stability,chemical stability and wear resistance.Due to carbon nanotubes?CNTs?unique mechanical properties,which combined with their high aspect ratio and nanoscale dimensions makes them excellent candidates for composite reinforcement.In this paper,flame spraying technology is used to prepare PEEK coating on 17-4PH stainless steel substrate through different substrate preheating temperature and spray gun moving speed,and PEEK/CNTs composite coatings with different dispersion conditions and compositions were prepared under optimal process parameters.Using scanning electron microscope?SEM?,fourier transform infrared spectroscopy?FTIR?,X-ray diffraction?XRD?,differential scanning calorimetry?DSC?analytical characterization methods to optimize the process parameters of flame sprayed PEEK coating,studying the effect of temperature on the structure and properties of the coating during flame spraying.Studying the effects of the dispersion of CNTs on the microstructure,crystallization behavior,chemical structure,bonding strength,microhardness and friction and wear properties of the composite coatings.Process parameter optimization results show,during the spraying process,the polymer chain of PEEK breaks and forms saturated alkanes and aromatic aldehyde functional groups.No significant change in surface roughness of PEEK coating.When the preheating temperature of the substrate is 200°C and the speed of the spray gun is300 mm/s,the porosity of the coating reaches a minimum of 0.775%,the bonding strength reaches the highest level,and the microhardness reaches the highest value of27.58 HV_0.5.The PEEK coating has a coefficient of friction of 0.446 and a specific wear rate of 12.3 x 10^-6 mm³/Nm.CNTs reinforced PEEK composite coating results show,the SEM analysis show that the dispersion of CNTs was improved after ultrasonication in anhydrous ethanol solution,which led to a significant decrease in the internal porosity and surface roughness of the composite coating.FTIR analysis showed that the relative content of two newly formed functional groups in the composite coating changed due to the high thermal conductivity of CNTs and many defects on the surface.DSC and XRD analysis showed that the poor density of CNTs reduced the nucleation density of PEEK and led to the increase of PEEK grain size,when the dispersibility is improved,the action of inhibiting the movement of the polymer chain and acting as a nucleating agent cause the PEEK grain to decrease.The dispersion of CNTs has no effect on the bond strength of the composite coating,and all are the highest level.Increasing the interfacial bonding between CNTs and PEEK makes the load transfer more efficient,resulting in a maximum increase in the hardness of the composite coating to 30.49 HV_0.5.In addition,the plastic deformation,crack and surface shedding on the surface of the wear scar are reduced,and the wear resistance of the composite coating is improved.Compared with the pure PEEK coating,the friction coefficient is reduced by 15.35%and the wear rate is reduced by 76%.