Papers by Author: Yu Zhou Gao

Abstract: Two kinds of ceramic additives have been developed that one is the serpentine particles and another is a blend of serpentine particles and catalyst. The tribological properties of the addition of different additives are investigated through a series of friction and wear experiments. Wear surface and the composition of the tribofilm were examined by SEM, EDS and XPS. In case of single serpentine additive, tribo-film can be formed gradually on the worn metal surface. The friction coefficient is about 0.11. The tribofilm mainly consists of Mg and Si elements transferred from the additive. This can compensates part of wear mass loss, avoids the direct contact of the two rubbing surfaces, and thus effectively improves the anti-wear characteristics. In case of the blend oil additive, the tribo-film formed obviously on the worn surface in the initial stage and no obvious film at end of the test. However, the friction coefficient can lower even to 0.007~0.008 compared with the above experiment. The worn surface becomes very smooth. Chemical analysis shows that there is a very thin film of carbon concentration with thickness of 30~50nm on the worn surface. Existence of the very thin carbon-concentrated film and mirror-like surface generates super low friction coefficient.

Abstract: The characteristics of the 1045 steel pairs using serpentine particles as grease lubricant additive were investigated by an AMSLER friction and wear tester. The surface topographies and composition of the worn surface of 1045 steel rings were identified by SEM and XPS. The results show that the additives can form a self-repairing film on the worn metal surface. It can reduce the abrasion of the friction pairs significantly. The main elemental compositions of the film are Fe, O, Si, C and Mg, which indicates that the additives directly take part in the formation of the self-repairing film.

Abstract: The work aims to investigate the anti-corrosion behavior of silane treated LY12 aluminum alloy (AA LY12) and optimize the process conditions of silane treatment. The silane films were prepared on AA LY12 from γ-aminopropyltriethoxysilane (γ-APS) hydrolized in ethanol/water mixture by dip coating method. The optimum process parameters were obtained from the orthogonal designs in terms of silane solution concentration, ethanol/water ratio, dipping time, curing temperature and curing time. Prior and after silane treatment, the surface of AA LY12 was characterized by contact angle measurements and scan electron microscopy (SEM). The potentiodynamic polarization tests and electrochemical impedance spectroscopy measurements (EIS) were employed to study the anti-corrosion characteristics of silane films on AA LY12. The impedance plots were fitted with the different equivalent circuits. Furthermore, the influence of the above process parameters of silane treatment on film formation and anti-corrosion performance was explored. The results indicate that the γ-APS treated AA LY12 significantly improved the corrosion resistance, compared to the untreated one.

Abstract: Sliding experiments lubricated with hydroxyl silicate magnesium particles as additive were performed under ambient condition and different loads by using an AMSLER friction and wear tester. The surface topographies and compositions of worn surface of 45 steel rings were analyzed by SEM and EDAX. The experimental results show that the friction load had great effect on generation of the frictionally-formed protective coating. No protective coating formed on the worn steel surface under lower friction load. However, a smooth and continuous protective coating can be developed on the worn surface of the steel when the friction load is high enough. The chemical composition of the protective coating is roughly the same as the additive. The additive can be fractured, stretched and flowed along the sliding direction under high contacting stress and instantaneous flash temperature, which result in coating being formed.

Abstract: Cavitaion erosion behavior of cast iron in water and in mixed solution of 50% H2O+50% C2H6O2 with different temperature and distance between two samples have been studied by means of a ultrasonic vibrator. The mass loss of the samples at different time is recorded.The surface structure of the oxidation films on the surface of cast iron was analyzed by X-ray diffraction apparatus. The experimental results show that mass loss of the upper sample is more than that of the lower sample. The maximum of mass loss occurred when the distance between the samples is about 1.0mm. Oxidation films form on the surface of the cast iron in pure water and cannot form on the surface of cast iron in mixed solution. The XRD results show that the oxidation film mainly consists of Fe2O3 phase at 50°C, Fe3O4 phase at 80°C. The mass loss at 50°C is less than that at 80°C. Oxidation film of Fe2O3 phase has some advantages to decelerate the cavitation erosion. Mass loss of the sample of cast iron in mixed solution is less than that in pure water at 80°C. This phenomenon indicates that formation of the oxidation films plays a more important role in cavitation erosion to reduce or increase mass loss of the cast iron samples.

Abstract: With excellent wear resistance and corrosion resistance of films, simple procedures, high production efficiency and being environmentally friendly, micro-arc oxidation has become a novel technique to produce ceramic coatings on the surfaces of light metals such as aluminum and its alloys. In order to decrease the electric power consumption during the process, we put forward a improved technique of micro-arc oxidation, and introduce its technical properties and treatment effects on the surfaces of aluminum. The experimental results show that the properties, such as phase structure, thickness, roughness and hardness of the ceramic coating prepared by improved micro-arc oxidation are similar to those prepared by traditional micro-arc oxidation. The micro-arc oxidation with higher deposition efficiency will be an important research direction in the future.