Study On Thermal Characteristics And Rolling Friction Of DLC Film On Surface Of Ceramics

The lubricant sources of self lubricating ceramic bearings include composite cages of self lubricating, the lubricating film of raceway surface modification and rolling surface modification. The widely application of silicon nitride ceramic ball bearing that without cages results in increasing need of lubrication with rolling surface modification. Diamond like carbon film, which was regarded as a solid lubricant with high wear resistance, low friction coefficient, high hardness and high chemical stability, was widely used in aerospace. However, under high temperature working condition, load carrying capacity of ceramic surface lubricating film not only have a great relationship with mechanical stress, but also with the interface thermal stress resulting from working process.By constructing contact mechanics, fracture mechanics and thermodynamics models, applying experimental analysis and simulation methods, this dissertation studied thermal characteristics ceramic surface DLC film, which contain the changes in the mechanical properties and effects of rolling friction after experiencing different temperatures cycling, sliding friction and wear properties at high temperature. These studies provide foundation for applications of modification film on the ceramic surface.Film adhesion is the bases of the silicon nitride ceramic surface DLC film working as lubricant, and the adhesion must be maintained under the effect of the heat. With nanometer indentation and scratch tests, bearing capacities and adhesion force between DLC film and the base are analyzed. The DLC films on the surface of ceramics plate and ball have experienced thermal cycles at different temperatures under positive pressure and shear force, and analyze the changes in the mechanical properties of the DLC film which were experienced thermal cycles at different temperatures. The dissertation provides theoretical basis for practical application of DLC films on silicon nitride ceramic.The model of Ansys finite element was employed to simulate the size and distribution of thermal stress of thin films under different working temperatures. By applying High Temperature Tribometer and selecting peoper experiment parameters, this dissertation studied the DLC film's tribological behavior under, different temperatures, loads and speeds, analyzed the wear mechanism under different conditions, got optimum temperature ranges in which DLC film can well perform as the lubricant, and obtained the critical load and critical speed at high temperature. Combined with the heat stress results from finite element model, the thermalload characteristics of DLC films was analyzed, which provides the theoretical basis for the DLC film's application at high temperature.Finally, bearing's friction torque was calculated based on the empirical model, dynamic friction torque of the coated ceramic ball bearing was tested with the tester of BRG3000 Torque, the effect of rolling friction DLC films was studied by comparing the friction torque at different lubrication and experimental parameters, which provides the application and evaluation tools for DLC films'application in bearings.