Papers by Author: Jian Li

Abstract: The low temperature deposition principle of magnetron sputtering was discussed. Reactive magnetron sputtering technique was used to gain titanium nitride (TiN) thin films on W18Cr4V high-speed steel substrates at low temperature. A series of experiments had been conducted to study the properties of TiN films. The experimental results showed that at the low temperature(<140 °C), magnetic sputtering can be used for the deposition of TiN film with compact, uniform and high nano-hardness, and their tribological properties were excellent, which co-determined by the film structure of low temperature magnetron sputtering and the counter-parts of rubbing pairs.

Abstract: Dry sliding tests with electric current were carried out on a pin-on-disc system tribometer in this study, where copper-base powder metallurgy material and copper alloy QCr0.5 were used as the pin and the disc respectively. The researches were aimed at exploring relation between tribological properties and current stability of the couple under different loads. The results indicate that the current stability and friction coefficient increases with current and load. Moreover, co-effect between the current stability and tribological behavior has been found, which behaves in the way that the higher the current stability, the higher dynamic current collection capability and tribological properties.

Abstract: Recent researches have found that surfaces with non-glazed or laser dimpling topography offer improved lubricating efficiency and wear resistance under lubrication conditions over their conventional glazed status. It was carried out in this paper to simulate a pin-on-disk experimental condition and perform hydrodynamic lubrication (HL) calculations for both non-glazed and glazed surfaces under conditions of different sliding velocities and loads with a view of understanding the tribological mechanism and characteristics of non-glazed surfaces. The results showed that the minimum film thickness of non-glazed surfaces, which closed to a typical elasto-hydrodynamic lubrication (EHL) film thickness, was thicker than that of glazed surfaces under the condition of low sliding velocities and small loads. At the same time, a decreased maximum pressure of full-film of non-glazed surfaces demonstrated an even pressure distribution on them.

Abstract: Ultra high molecular weight polyethylene (UHMWPE) is a kind of non-polar polymer with a crystalline structure. Its failure appeared usually as a type of wire drawing when it was used as a material of rubbing pairs. By a designed heating test, the thermal damage phenomena of UHMWPE were observed by SEM. Its thermal damage model during the process of wire drawing damage was assumed that when the thermal energy was accepted by the UHMWPE, its volume expanding and its surface melting into a viscous fluid proceeded from its elevated temperature, and then the viscous fluid flowed according with non-Newtonian fluid model; after cooling, the melt re-crystallized and gathered again and at the same time many obvious cavities with phenomena of wire drawing appeared in the re- crystalline polymer. As a result the material of UHMWPE shrank to porosint from the congeries with the small uniform particles.