Study On Toughness And Tribocorrosion Properties Of Gradient Nano TiSiCN Coatings

Marine high and new technology plays an important role in the development of China’s national economy and military forces.While exploiting marine resources,there is also a huge challenge for how to prolong the service life of special equipment in the marine working environment.Therefore,some materials with better mechanical properties,abrasion resistance,corrosion resistance and even some special functions have born on demand.The protective coating constructed by PVD technology is considered as one of the best ways to improve the life and stability of marine equipment,and is widely used on the surface of marine equipment parts.With the increasing performance requirement,its structure has developed from traditional binary structure to multi-layered or even gradient structure,among which multi-layered nano-composite coating with gradient structure has become one of the research hotspots in the field.Multi-arc ion plating technology is currently the main preparation technology of gradient structure coating,but the problems of poor strength and toughness,noncorrosion and limited use of lubricating oil in seawater environment are still one of the key problems to prolong the service life of high-end marine equipment.In this thesis,in order to solve the urgent need of developing marine equipment,the gradient design concept of composition-structural scale-elasticity performance was innovatively put forward,and multi-arc ion plating technology was used to prepare gradient nano-Ti Si CN coatings with self-lubricating properties.The microstructure and properties of coatings with different C content were systematically studied in this thesis,and a group of ordinary Ti Si CN coatings were added as a control.It was found that the C content in Ti Si CN coating increased with the increase of acetylene flow rate in the deposition atmosphere,and with the increase of C content,the compactness of the coating increased,and the gradient structure effectively interrupted the coating defects.With the increase of C content,the hardness and elastic modulus of the coating decreased,but the self-lubricating property improved significantly.In the Ti Si CN coating with the same carbon content,the gradient coating has higher H/E and H3/E2 values,which improves the strength and toughness.The friction and wear properties of the coating were also studied.The gradient Ti Si CN coating with C content of 24% and32% had spalling failure under 10 N load.The gradient coating with C content of 40%showed excellent self-lubricating ability in the friction process.It reflected in the appearance of wear marks was smooth,without obvious spalling failure,and excellent abrasion resistance.The ordinary control group with the same C content had partial spalling failure,and the gradient wear rate decreased by about 30%.The corrosion resistance of the coating in simulated seawater environment was studied.The gradient Ti Si CN coating with C content of 24% and 32% had serious pitting corrosion,and the gradient coating with C content of 40% effectively interrupted the penetrating defects in the coating and prevented the corrosive medium from corroding along the boundary of the defects.Compared with the control group with the same C content,the gradient structure can reduce the corrosion current density by about 41% and increase the polarization resistance by about 88%,which has the best corrosion resistance.In this thesis,by adopting the combination of systematic test and micro-scale analysis,the growth law and phase composition of gradient self-lubricating coating are revealed by,and the influence of gradient process on coating structure is expounded.The mechanical properties of the gradient self-lubricating coating and the failure law in the process of friction and wear are revealed,and the influence of gradient technology on the mechanical properties and self-lubricating properties of the coating and the wear mechanism are expounded.The electrochemical performance law of gradient selflubricating coating was revealed,and the influence of gradient process on the corrosion resistance of coating and its corrosion resistance mechanism were expounded.The data results further showed that gradient process could effectively refine the grain and make the coating dense with the same C content,with strong self-lubricating ability,reduce the friction coefficient and wear rate,improve the corrosion resistance of coating and prolong the service life of coating.The research results provide a new choice for the development of new marine self-lubricating protective coatings.