Study On Toughness And Corrosion Wear Resistance Of Nano-multilayer Coatings

Marine resources are abundant in our country,and it is urgent to develop the marine resourcesin the absence of terrestrial resources.However,seawater is rich in various elements and highly corrosive.In addition,wear and corrosion synergies between most parts of marine equipment areinevitable.Together with fluid erosion,material working conditions are harsh,resulting in equipment failure,stability reduction and short service life.Therefore,improving the corrosion and wear resistance of materials is a key issue in the development of marine engineering.Ceramic coatings have the advantages of high hardness and corrosion resistance,but their inherent brittleness seriously restricts their wide application.In this paper,ion-assisted unbalanced magnetron sputtering was used to successfully prepare CrSiN/SiN nano-multilayer films and CrN/AlN nano-multilayer films with different structures.The structure,mechanical properties,toughening mechanism electrochemical performance and corrosion wear behaviorof the two coating systems were studied.The main conclusions are as follows:（1）With the modulation period decreases,the CrSiN/SiN nano-multilayer coatings structure becoming denser,because the multilayer coatings interface interrupts the columnar growth of the coatings.The CrSiN/SiN nano-multilayer coatings withΛ=45nm has the highest hardness and elastic modulus,and the K_IC value increases with the modulation period.The multilayer film structure improves the toughness of the coating.The corrosion current density of CrSiN/SiN nano-multilayer coatings withΛ=90 nm andΛ=360 nm are reduced by three orders of magnitude compared to that of TC4titanium alloy,reaching 10^-8 A·cm^-2.Among them,the CrSiN/SiN nano-multilayer coating withΛ=45 nm has the lowest wear rate of 9.67×10^-7 mm³·N^-1·m^-1.The wear mode is mainly abrasive wear,and the surface of allthe coatingsare peeled off.The CrSiN/SiN nano-multilayer coatings effectively improve the overall performance of the TC4 titanium alloy substrate.（2）AlN in the CrN/AlN nano-multilayer film with AlN sublayer thickness of 3 nm exists in the metastable cubic structure,and AlN in the CrN/AlN nano-multilayer film with AlN sub-layer thickness of 10 nm is stablein hexagonal structure.The comprehensive mechanical properties of the former are better than the latter.The CrN/AlN nano-multilayer films with different thicknesses of AlN sub-layers have lower corrosion current densities than 304 stainless steel during static and sliding corrosion,mainly due to the destruction of columnar crystal structure at the interface of the multilayers,makeing it difficult for the solution to enter into direct contact with the coating and the substrate.The CrN/AlN nano-multilayer film with AlN sub-layer thickness of 3 nm has the best corrosion wear performance.Since crack defects tend to occur at the interface,the incoherent interface is weaker than the coherent interface.In addition,the strain-induced phase transition with a volume expansion ratio of about 26%can release the compressive stress by external strain during the sliding process,thereby inhibiting crack propagation.Therefore,the corrosion and wear resistance of the CrN/AlN nano-multilayer film is improved.（3）Corrosion and wear synergy during corrosion and wear process.To a certain extent,the wear rate of the coating has a certain relationship with the toughness.Without sacrificing the hardness of the multilayer film,increasing the toughness can improve the tribocorrosion of the coating,and the wear rate of the coating is inversely proportional to the toughness.