Research On PTFE/PEEK Coatings For Lubrication Improvement Of Wrist Pin In Oil Free Piston Compressor

PTFE/PEEK (Polytetrafluoroethylene/Polyetheretherketone) polymer coating has extensive prospect of application due to its unique hybrid properties, such as self-lubrication, high wear resistance, corrosion resistance, radiation resistance and great chemical stability. As higher demands of clean compressed air, the oil free compressor had come out. The wrist pins in this compressor are lubricated by grease which is limited in some cases, such as the failure and leakage of grease or evaporation in vacuum, so that they cannot meet good or stable lubrication totally. Therefore, in this thesis, PTFE/PEEK coating was invited to improve it by taking the place of grease for better performance of oil free compressor and expanding its scope of application.Firstly, an oil free air compressor was designed to obtain the parameters for PTFE/PEEK coating tests on SRV tribometer.Secondly, PTFE/PEEK coatings were prepared by electrostatic powder spraying method and factors were investigated on the preheating temperature, coating thickness and working temperature by the orthogonal experimental method. The results show that250℃preheating temperature,100μm-150μm coating thickness and150℃working temperature are better conditions for playing good performance of PTFE/PEEK coating. For the influence of stroke, in the range of coating thicknesses from20μm to150μm, the COF values are not influenced too much by strokes as the increasing of coating thickness, and bigger strokes can obtain lower COF values.Finally, ANSYS was used to build a transient thermal model to analyze the temperature distribution in two working conditions-the fixed wrist pin and the rotated wrist pin. The results show that the first stage can meet the better conditions which are obtained by tribological tests, and the second stage cannot. Also, the temperature distribution becomes uniformity as wrist pin rotated, which can limit the thermal stress.The conclusions in this thesis prove the feasibility of application of PTFE/PEEK coating, and provide a new design method of oil free compressor using polymer coating lubrication, and provide a reference of PTFE/PEEK coating application.