Preparation Of Graphene Composite Coatings And Study On Their Wear And Corrosion Resistance

The purpose of this paper is to prepare a solid lubricating coating with both wear resistance and anti-corrosion properties,which used to improve steel-steel spherical plain bearings'tribological and corrosion resistance properties.Graphene is currently the newest nanomaterial with the highest hardness.Graphene is both a good solid lubricant additive and an ideal anti-corrosion material because of its unique crystal structure,special self-lubricating properties,and good water vapor barrier properties.Using MoS₂ as a lubricant,graphene(GE)as an additive and BYK-9076 as dispersant,GE/MoS₂ composite coatings with different graphene additions were prepared on GCr15 steel samples by spraying.After adding graphene,the elastic modulus and microhardness of the pure MoS₂ coating was improved.Both of them increased first and then decreased with the increasing of the addition of GE;when the addition of GE increased to 1.0wt%,the density of the coating decreased,its surface roughness also increased significantly.The tribological performance of the GE/MoS₂ composite coating with different graphene additions in dry friction and seawater environment was tested by HSR-2M type ball-plate speed reciprocating friction and wear tester.The wear mechanism was analyzed by the scanning electron microscope(SEM)and energy dispersive spectrometer(EDS).The tribological properties of 0.8-GE/MoS₂ were the best,and the coefficient and wear amount under dry friction were 0.232 and 0.0535mm³ respectively,in the seawater environment were 0.224 and 0.025mm³ respectively.And the tribological performance of different coatings in seawater environment are better than the dry friction condition.The contact stress,sliding speed and coating additive raw material forms were selected as the factors,the friction coefficient and wear amount of the coatings under dry friction and artificial seawater were used as evaluation indicators,through orthogonal test,the gray correlation analysis method based on the combination weighting method is used to process the test data.The higher the correlation degree,the better the comprehensive tribological performance of the coating.Then the optimal test conditions and coating formulations were selected by the average correlation degree of each level.The variance analysis of the gray correlation of the orthogonal test was obtained,and the significant effect of the different factors impact on the comprehensive tribological properties of the graphene/MoS₂ composite coating was obtained in the order of additive raw material>contact stress>sliding speed.Electrochemical workstation and neutral salt spray test were used to research the anticorrosion performance of the coatings.Comparing with pure MoS₂ coating,the self-corrosion potential of the GE/MoS₂ composite coating is significantly more positively shifted,the anode slope increased,the self-corrosion current density decreased,and the duration of salt spray resistance is also obvious increased;the composite coating with 0.8wt%GE has the best protection performance for GCr15steel substrate,and its self-corrosion current density was reduced by nearly 2 orders of magnitude compared with pure MoS₂ coating.