Papers by Author: Dun Wen Zuo

Abstract: To study effects of nano-Al2O3p (nanometric Al2O3 particles) on high temperature frictional wear behaviors of the NiCoCrAlY coating (a high temperature protective coating), three NiCoCrAlY coatings strengthened by different contents of nano-Al2O3p were prepared on a Ni-based super alloy by using laser cladding technology and their dry frictional wear behaviors at 500 °C in static air were investigated. The comparison was made with the coating without nano-particles. The results show that the frictional coefficient of the coatings increased with the hardness after adding nano-Al2O3p and the wear resistance of the coatings was enhanced. Among nano-Al2O3p-added coatings, the coating added with 1.0 wt% nano-Al2O3p performs best. The wear rate of the coating is only 58% of the coating without nano-particles. Moreover, the improvement of the oxidation behavior plays an important role in improving the high temperature wear resistance.

Abstract: The diamond coatings were prepared by hot filament chemical vapor deposition(HFCVD) on the mono-crystalline silicon substrates. The influence of the technical parameters such as methane volume ratio, substrate temperature and reaction pressure on the residual stress in the diamond coating was studied. The results showed that the residual stress in the coating was compressive stress in the range of parameters studied, and too high or too low substrate temperature, chamber pressure and methane volume ratio would all increase the residual compressive stress. This relationship can be explained by the influence of amorphous carbon content, vacancy density and grain size on the residual stress.

Abstract: Diamond coatings were prepared on mono-crystalline silicon by hot filament chemical vapor deposition (HFCVD). Hardness, elastic modulus and other mechanical properties of the diamond were analyzed by nanoindenter. The results showed that the process parameters such as chamber pressure, substrate temperature, methane volume ratio have a greater impact on the mechanical properties of the diamond coating. The micro-hardness and elastic modulus of the coating would both decrease with too high or too low substrate temperature, chamber pressure or volume ratio of methane. The results showed that when the substrate temperature is 750°C, champer pressure is 2.5kPa and methane volume ratio is 2%, the diamond coatings have high micro-hardness and elastic modulus.

Abstract: Formulae of stress re-distribution and distortion by stress releasing during milling process are deduced to Initial Residual Stresses. Theory prediction of milling deformation due to residual stress is finished, and some calculating equation is given for the deformation solution. By means of these researches, the mechanism of the milling deformation due to residual stress is analyzed, the machining distortion caused by residual stress are analyzed and summarized using the analytical method.

Abstract: The performance of Atomic Force Microscope (AFM) is greatly determined by the quality of its probe. Nowadays, probes of diamond tips have become more and more popular than silicon ones, and have been widely used in industries. In this paper, research about the fabricating of nanocrystalline diamond (NCD) coated AFM probe has been done using Hot-Filament Chemical Vapour Deposition (HFCVD) technique. The results showed that NCD films have been grown on the probe. Problems about the growth of NCD on the tips have been discussed. The optimum parameters have also been proposed. This research can provide reference for the further experiments on the fabrication of NCD coated tips.

Abstract: The optical-grade diamond film was prepared by DC plasma jet CVD method, and a double-sided polishing was made by EDM and mechanical polishing technology. The investigations of the internal stress at different temperature on the infrared transmission were tested in detail. SEM and AFM were used to study the polished surface morphology, surface roughness was 0.12nm and 0.25nm. XRD and Raman were characterized on the diamond films, the results showed a higher intrinsic quality. The internal stress distribution and infrared transmittance were investigated at 25°C and 100°C temperature respectively. The infrared transmission mechanism of diamond film was also discussed. The main reason of decreasing of infrared transmittance was the increasing grain collisions, which caused more scattering and absorption of incident light with temperature increasing.

Abstract: The contact stress of cemented carbide with NCD coating in elastic contact was analyzed using ANSYS. Factors such as elastic modulus and thickness of NCD film and elastic modulus of interlayer which affect the shear stress distribution of NCD film on cemented carbide substrate were investigated. The results show that the maximum shear stress point moves towards the interface with the increase of film elastic modulus. Film thickness has a significant effect on shear stress distribution of NCD film. High shear stress develops in the film layer with the increase of film thickness. Interlayer with low elastic modulus will cause shear stress concentration in NCD film.

Abstract: A kind of model oriented assembly process simulation in WTK environment has been proposed. In the model, firstly, the assembly hierarchy of mechanical products can be presented clearly. Secondly, the assembly constraints between parts can be added to the model easily. At last, the assembly process information such as assembly sequence and path for each part can be recorded at real time in the model. Then, the converted method from PRO/E system to WTK environment about the mechanical product’s design information including geometric models, product design hierarchies and constraints has been discussed, which makes for easier building the model in the virtual environment.

Abstract: The green fixture is the research focus, but the current research is centralized on the fixture driven by the air. It will lead to a noise polution and a small clamping force. Using the green electromagnetic conversion technology, a new clamping system to clamp the workpiece is provided, which is composed of the giant magnetostrictive material as working medium and the displacement amplifier with the area effect. This device can realize the flexible configuration of clamping at multi-place, for multi-workpiece and in multi-direction. Furthermore, this clamping system using the A/D converter and the sensor technology of pressure and displacement to collect the relative data, the collected data can to be putted in the computer and be processed，so it is easy to control the clamp force and clamping displacement intelligently.

Abstract: The magnitude and the uniformity of the substrate temperature are the most important factors that affect the quality and the growth rate of diamond films deeply. In this paper, the model of the swing substrate temperature field is established according to the heat transfer theory in Miniature EACVD System, the effects of the hot-filament parameters and the substrate swing parameters on the magnitude and uniformity of the substrate temperature were discussed. The calculated results show that the hot-filament parameters have great influence on the magnitude of the substrate temperature , the results also show that the hot-filament number , the substrate swing angle and the distance between the hot-filament and the substrate affect the uniformity of the substrate temperature field deeply. All the results provide a basis for optimizing the parameters of deposition in Miniature EACVD System.