| Self-lubricant coatings are special functional materials with self-perception and self-actuation properties.It is a key technology related to the development of major national engineering tasks.In the past,intelligent lubricant coatings were usually prepared in the form of a composite of amorphous and nanocrystalline.However,there are many defects in this design method.For example,the mismatch between the layers of the coating will cause premature failure;multiple atmospheres during deposition not only complicate the process but also reduce the life of equipments;and it was difficult to regulate the components of the coating in an orderly manner.Therefore,this thesis proposes a new construction scheme for self-lubricant coatings,which selects TiN as the substrate carrying solid lubricant,enhances the self-shadowing during deposition by combining arc ion plating with oblique angle deposition,prepares a TiN coating skeleton with a regular array structure of"melt pool",and finally constructs a composite intelligent lubricating coating with both wear-resistant and lubrication functions by filling the lubricant phase inside the"melt pool".In this thesis,firstly,TiN coating with high hardness and wear resistance was prepared on 304 stainless steel and silicon wafers by AIP in different nitrogen pressure,focusing on the effect of deposition air pressure on the chemical composition and growth structure of the coating,and the mechanical and tribological properties of the coating were tested and analyzed;Subsequently,the structure of the TiN coating was modulated by a combination of AIP and OAD to obtain a titanium nitride"melt pool"skeleton with a columnar crystal structure and free separation between columnar crystals.The effect of working pressure on the structure,mechanical properties and tribological properties of the coating deposited by OAD was investigated compared to the TiN coating obtained by vertical deposition;Finally,the TiN-based self-lubricant composite coating was prepared by hydrothermal and high-temperature heat treatments,in which TiN with different structures and porosity was used as the matrix and glucose as the precursor.In order to investigate the tribological properties and lubrication mechanisms of the coating,wear tests were conducted on the composite coating.The results were as follows:Comparing with the TiN coatings deposited in three different working pressures of 0.27 Pa,0.5 Pa and 0.8 Pa,it was found that the coatings all had dense microstructures and high hardness.Increasing the working pressure can eliminate the columnar structure of the coating and further improve the mechanical properties.The maximum microhardness of TiN coatings was HV 2127.Wear tests showed that the friction coefficient of TiN coating under dry friction was about 0.8,and the wear rate reached as low as 2.9×10-7 mm3/（N·m）.The TiN coating prepared under 0.8 Pa nitrogen had the longest wear life.TiN coatings were prepared by OAD at the same working pressure.The results showed that the increase of deposition angle changed the coating from compact structure to loose columnar structure,and the crystal growth direction was all toward the incident direction of the target particles.Increasing the working pressure improved the surface porosity of the coating.The porosity of the TiN deposited in 0.8 Pa was13.7%.The existence of the nanopores increased the defects of the coating and sharply reduced the original mechanical properties and wear resistance of the coating.The porous TiN coating prepared under 0.8 Pa nitrogen had the highest hardness and wear life,which were HV 782 and 860 s,respectively.Composite coatings were prepared by hydrothermal and high-temperature heat treatment.EDS showed that the porous TiN coating prepared by OAD could store carbon effectively compared to the dense structured TiN coating,and the addition of carbon significantly reduced the friction coefficient from 0.9 to 0.35.Comparing the wear life of the composite coatings with different porosity of TiN coating as matrix,it was found that the coating with the highest porosity of 13.7%had the best tribological performance,which could maintained a friction coefficient of 0.35 for up to 8000 s.Raman was used to characterize the wear scars of the composite coating.The results showed that the coating with"melt pool"structure characteristics can quickly reconstruct the surface structure when subjected to wear,i.e.,the carbon lubricant phase stored in the nanopores continuously enriches to the friction contact area and intelligently builds up the surface layer,forming a low-shear carbon film in the friction contact area,thus achieving long-term anti-friction and lubrication. |
