Design and Preparation of Element Doping Carbon-Based Thin Films for Marine Atmosphere Environment Applications

Author:Zhan Hua

Supervisor:wang wei ping wang rui jun


Degree Year:2018





The carbon-based thin film material has a very low coefficient of friction under dry friction conditions and has a strong chemical stability in a corrosive environment.As a protective film,it can effectively reduce the wear loss of the material and avoid external corrosion.With the development of research,it has been found that carbon-based thin films can reduce the abrasive failure of metallic materials in seawater environments,but there is a weakness of relevant research on the tribological properties of carbon-based thin films in marine atmospheric environments.This paper focuses on the study of carbon-based thin film for the marine atmospheric environment applications.A marine corrosion environment friction and wear testing machine was designed and set up.Using this test machine,the corrosion and wear mechanism of carbon-based films were studied.According to the failure mode analysis of carbon-based thin films under marine atmospheric corrosion conditions,a multi-layered gradient element doped carbon-based thin film was designed and prepared.The carbon-based thin films that can be used in practical engineering in the marine atmosphere are obtained through the optimization of the process parameters of thin film preparation.It is prepared on the surface of a certain type of aircraft folding mechanism,which successfully solved the problem of function failure of the component and verified by test flight.The main research contents and conclusions of this article are as follows:A marine corrosion environment friction and wear tester was designed and set up,and the friction and wear properties of the material under conditions of salt spray corrosion,seawater corrosion,and coupling load,temperature,and rotational speed were evaluated.The friction and wear behavior of carbon-based thin films under salt spray corrosion was tested using the corrosive friction and wear tester.By analyzing the friction coefficient curve and the appearance characteristics of worn wear scars,the failure model of carbon-based thin films under sliding contact in a corrosive environment was revealed.The model mainly includes material surface coupling and capillary action increase,the ploughing effect caused by oxidation/corrosion products,and the pitting caused by micropores on the surface of the carbon-based thin films.The combind action of the three causes premature failure of the carbon film.A new type of composite gradient film structure has been designed and verified.The performance comparison test was conducted by the marine corrosive environmental friction and wear tester.It was found that CrN is a transition layer of carbon-based films with better properties than TiN transition layers of carbon-based films,including film/base bonding strength,corrosion resistance,and wear resistance under dry friction and salt spray friction conditions.Compared with the properties of tungsten-doped and chromium-doped carbon-based films,it was found that the content of sp3 hybridized bonds of tungsten-doped carbon-based films was higher than that of chromium-doped carbon-based films.The film/base bonding strength and hardness of tungsten-doped carbon-based films are also higher than those of chromium-doped carbon-based films.The wear volume of tungsten-doped carbon-based films under dry friction and salt fog corrosion friction conditions was 7.12×10-4mm3 and 361×10-4mm3,respectively,which were lower than those of chromium-doped carbon-based films.Based on the above comparative test results,the structure of the thin film was finally determined.The tungsten-doped carbon-based thin film was used as the functional layer of the composite gradient film,and the gradient transition CrN thin film was used as the intermediate transition layer.The relationship between preparation process parameters and film properties was studied.Four kinds of Cr-CrN transition layer films with different thicknesses were prepared using a multi-functional ion deposition deposition system.Through comparative tests,it was found that when the Cr layer thickness is 0.36 μm and the CrN layer thickness is 1 μm,the surface pore sizes of the film is the smallest and has the lowest friction coefficient and best wear resistance.Tungsten-doped carbon-based films with different tungsten contents were prepared by adjusting the tungsten target current.It was found that the content of tungsten in the films increased with the increasing the tungsten target current.When the content of doped tungsten is low,the film had low film/base bonding strength,high hardness,and good abrasion resistance under dry friction conditions,but poor wear resistance under salt spray corrosion conditions.When the content of doped tungsten is 8 at%,the film had the best film/base bonding strength,the lowest internal stress,and was good tribological performance under both dry friction and salt spray corrosion conditions.In addition,composite gradient multi-layer tungsten-doped carbon-based thin films with four different layers and thickness transition layers were prepared and compared.It was found that the CrN/CrCN/W-DLC(W-DLC-2 layer)film has the lowest friction coefficient,the smallest amount of wear,and the least oxidation/corrosion product under salt spray corrosion conditions.In view of the urgent need for the short marine service life of the connecting mechanism of a certain type of aircraft folding mechanism,the above-mentioned gradient multi-layered tungsten-doped carbon-based thin film was prepared on the surface of the connecting rods.After the ground environment test and 1500 ground reliability disassembly tests,the carbon-based film was intact.Up to now,20 sets of connecting rods have been tested for installation flight tests,and failures in disassembly and assembly jamming have not occurred.In summary,the research work in this paper provides theoretical support and technical support for the safety and reliability improvement of structural metal materials in marine atmospheric environment in our country.