Fabrication And Properties Of Al₂O₃-based Wear-Resistant Hydrophobic Non-stick Coatings

In order to develop novel hydrophobic?non-stick?coatings with independent intellectual property rights,develop advanced fabrication techniques,improve the comprehensive performance of coatings,and broaden application range of them,this study selected PFA as raw material.Which was filled and modified with Al₂O₃,Al₂O₃-40%Ti O₂?AT40?ceramic powder,and the powders were mixed by mechanical mixing.Atmospheric plasma spraying?APS?was used to prepare wear-resistant composite hydrophobic coatings on aluminum substrates.And the effect of the mixing ratio and spraying parameters on the coating performance were investigated.At the same time,composite coatings were heat-treated.The structure,composition and phase composition of coatings were characterized by XRD,SEM,EDS and other methods.The corresponding equipment and test methods were used to measure or evaluate the microhardness,bond strength,roughness,surface static contact angle,and friction of coatings.As the results,discuss the movement mechanism and deposition mechanism of powder particles in the plasma flame flow,analyze the hydrophobic and frictional damage mechanism of the coating surface.The details are as follows:?1?Composite coatings were prepared by APS with a mass ratio?Al₂O₃:PFA?of4:1 and 3:1.Composite coatings are mainly composed of?-Al₂O₃.Meanwhile a small fraction of?-Al₂O₃ and fine crystals or amorphous crystals are also found in coatings.PFA particles are embedded in the alumina with a granular or block shape,forming composite structure.The bonding strength of coatings under the optimal parameters is co MParable to the bonding strength?about 30 MPa?of the common Al₂O₃ ceramic coating which prepared by APS.The microhardness and the contact angle is 670 HV _0.1,129.1°respectively.?2?The friction and wear processes have both of adhesion and abrasive wear.The wear rate of the coating is less than 10 mm³/N·m,reduceing significantly co MPared with the single polymer?45 mm³/N·m?.Composite coatings have also good corrosion resistance.?3?Composite coatings were prepared by APS with a mass ratio?AT40:PFA?of1:3.And increase AT layer as transition coating.Composite coatings are mainly composed of C₂₀F₄₂,Al₂Ti O₅.Meanwhile a small fraction of?-Al₂O₃ and?–Al₂O₃ are also found in coatings.?4?The surface structure is composed of circular and oval granular structure,and micro-nano mastoid structure was found,which similar to the lotus leaf.Granular structures are mostly composed of PFA paticles with low surface energy,and smaller size ceramic particles are distributed in junctions and surfaces.The bonding strength reaches15 MPa,and its microhardness is 110 HV_0.1.The angles are all more than 150°,the rolling angle is about 4°?5°,with super-hydrophobic and good corrosion resistance.?5?The coefficient of friction and wear rate of coatings were 0.09,0.12,20.21mm³/N·m,and 11.23 mm³/N·m,respectively.The friction and wear processes have both of adhesion and abrasive wear.And abrasive wear is obvious in the coating with a current of 590 A.?6?The Al₂O₃/PFA with a mass ratio?Al₂O₃:PFA?of 3:1 and AT40/PFA composite coatings were heat treated.The co MParison showed that the phase composition of coatings did not change,and the PFA in the coating remelted to form a uniform and continuous spreading on the surface.The quantity of Al₂O₃ particles in the Al₂O₃/PFA coatings which exposed on the surface are reduced,so that the surface roughness is increased,and the hydrophobicity is greatly improved,the coating contact angle under different parameters all can reach 140°,the maximum can reach 152°.Due to the original protruding structure and the dual micro-nano-small papillae decreased or even disappeared,the roughness of AT40/PFA coatings is decreased.The contact angle of them has decreased.?7?The bond strength and friction coefficient of the Al₂O₃/PFA composite coatings after heating treatment decreased slightly,the microhardness increased slightly,the wear rate increased,wear resistance decreased slightly.?8?The internal combination of the PFA/AT hydrophobic coating is changed from stacking to layer bonding.The porosity inside coatings is reduced.The microhardness of coatings will increase,therefore,the bonding strength of the coating with a spraying current of 590 A is improved significantly.However,the bonding strength of the coating with a spray current of 620 A showed a slight decrease,the friction coefficient showed a small increase,the wear rate decreased,the wear resistance is improved,and the corrosion resistance is improved.