| As a engineering technology,supersonic plasma spraying has been broad appied in the fields of component surface protection,modification and strengthening.However,due to the variability and complexity of coating surface in physical and chemical properties,a lot of association between performance and surface free energy has not been figured out.Therefore,further explore the inner link between the coating prepared by supersonic plasma spraying and surface free energy with its components has important practical signification for the application of the spraying technology.The study has prepared Cr2O3-TiO2 composite ceramic coating?CT coating?with dif-ferent TiO2 content by using two preparation techniques:supersonic plasma spraying?SPS?and the general atmospheric plasma spraying?APS?.In the study,the surface morphology,microhardness,phase composition,microstructure and surface free energy has been tested by scanning electro microscope,microhardness tester,X-ray diffraction,transmission elec-tron microscopy and the contact angle measuring instrument.Then,the friction property and contact fatigue property have been tested by the UMT-3 tester and RM-1tester.Final results showed that:?1?For the coating containing TiO2,the changing laws of friction coefficient and surface free energy have a consistency whether the condition is dry or oil-lubricated,they all show an increasing trend after the first reduce.The minimum appears at CT16 coating.The reason for this is due to the surface free energy will have an impact on the bonding re-sistance between the coating and friction pairs.If the coating has a higher surface free en-ergy,the bonding will appear easier during the course of friction between coating and fric-tion pair,leading to a hinder strength happened.So under the same load conditions,the coating with higher surface free energy will have a higher friction coefficient.Conversely,when the coating have a lower surface free energy,the bonding force between coating and friction pair will lower,so the relative movement will easier happen.Thus the friction coef-ficient shows low.?2?The variations of dispersive component and the polar component of surface free energy will have a certain degree of influence to the friction coefficient of the coating,and the friction coefficient of two states shows a good consistency with the change of free en-ergy components.Except the dry friction coefficient changes with the dispersion compo-nent showed a good sensitivity,the oil lubrication friction coefficient changes with the dis-persion component,dry friction coefficient changes with polar component and oil lubrica-tion friction coefficient changes with the polar component performance a poor sensitivity.Therefore,the impact on friction coefficient under the condition of dry friction and oil lu-brication is a result of the combined effect of surface free energy.?3?The change of surface roughness have an important influence on surface free en-ergy components,but for the influence of the coating surface free energy it is produced by the interaction of the two components.When the surface roughness of coating less than a certain value,the polar component rapidly reduces and gradually approaches to 0,then the dispersion component gradually stabilize,limited changes in amplitude.For the small roughness coating,its surface free energy is low,less porosity and micro-defects stored oil,so the cyclic high-pressure oil wave is small,low depth of the impact damage will happen and the damage parts lighter.?4?The contact fatigue life will extend with the surface roughness reduce.The main reason is due to the coating with smaller roughness has a lower surface free energy,and the surface of coating will adhere less lubricating oil.In the process of testing,the lubricating oil into coating micro defect decline.Thus the degree of shock by high-pressure oil wave is small.When the surface roughness is less than a certain value,the free energy change will have a greater impact on the contact fatigue life. |
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