Papers by Author: Hong Xiang Wang

Abstract: Coal-winning machine is to break coal with rotating mechanism. Owing to the harsh working environment and large stress, the top-disc plate, helical blade and tooth holder in cylinder often lose their wear resistance, hence causing overhauling of the machine and influencing the production of coal. With the modernization of the production technology and mining equipment of coal, the mining intensity of coal constantly increases, which calls for higher wear resistance of the top-disc plate, helical blade and tooth holder in cylinder. Currently, many studies have been performed on the wear resistance of the tooth holder in cylinder, but rare on the wear-resistant technology and wear resistance of the top-disc plate and helical blade in cylinder. In this paper, 16Mn steel which is used in the top-disc plate and helical blade in the cylinder of coal-winning machine was welded based on surfacing technology using EDTCrMnSi special wire to obtain composite wear-resistant steel plates. Then wear tester was employed to compare the wear of 16Mn steel and composite wear-resistant steel plate. Meanwhile, metallographic microscope and x-ray fluorescence spectrometer (XRF) were used to observe the microstructure of the materials and analyze the types and contents of elements in the surfacing layers of the composite wear-resistant steel plate. Furthermore, the influence of surfacing technology on the wear resistance of the material was analyzed. The results showed that there existed high contents of Cr, Si and Mn in the surfacing layers of the top-disc plate and helical blade in cylinder of the coal-winning machine after welded based on surfacing technology. Moreover, the wear resistance and service life of matrix were largely improved.

Abstract: In order to improve the high temperature oxidation resistance of exhaust pipes, the nanocomposite coatings are carried out on the surface of exhaust pipe by electrodeposition technology, and the microstructure and oxidation behavior of the nanocomposite coatings are investigated experimentally. This paper mainly focuses on the experimental work to determine the structural characteristics and oxidation resistance of nanocomposite coatings in presence of Al₂O₃ and cerium oxide CeO₂. The results show that the amount of the Al₂O₃-CeO₂ has significant influence on the structural properties of nanocomposite coatings. The surface of coating becomes more compact and smooth with the increase of the amount of the Al₂O₃ and CeO₂. Furthermore, the anti-oxidation performance of the nanocomposite coatings formed with Al₂O₃ and CeO₂ were both better than those of the composite coatings formed without Al₂O₃ and CeO₂.

Abstract: In order to improve the corrosion resistance of shock absorber for ships, the alumina ceramic coatings are carried out on the surface of aluminum alloy shock absorber by micro arc oxidation (MAO) technology. The microstructure and anti-corrosion performance of the MAO coatings were investigated experimentally. This paper mainly focuses on the experimental work to determine the effect of current density on the structural characteristics and corrosion resistance of MAO coatings. The results show that the current density has a significant influence on the preparation of MAO coating during the process. The surface of the coating becomes more compact and smooth with the cathode voltage of 7 A.dm^-2. Furthermore, the anti-corrosion performance of the MAO coatings can effectively be improved at the current density of 7 A.dm^-2.

Abstract: To solve the low transmission reliability in Internet of Objects monitoring system of facility agriculture, this study discussed the influences of transmission reliability in Internet of Objects. Meanwhile, the factors influencing transmission reliability of Internet of Objects were analyzed. Then, based on the results obtained, corresponding solutions were proposed. This research plays a guidance role in further improvement of reliability and function management level in Internet of Objects monitoring system.

Abstract: In this paper, the coating was prepared by the slurry pack cementation on the surface of Fe-14Mn-6Si-5Ni alloy at 900°C for 10 h. A slurry pack cementation mixture was composed of Cr₂O₃ used as chrominizing source, pure Al powder as reducer, an activator of NH₄Cl and albumen (egg white) as cohesive agent. The microstructure, wear resistance and corrosion resistance of coating has been studied. The results showed that the microstructure of the coating is composed of solid solution with Al and Cr; the microhardness of coating with a value of 460 HV was 1.4 time than that of the matrix alloy, friction coefficient of the coating was 0.35, 1/2 of that of matrix alloy, and the rate of corrosion of coating was lower one order of magnitude than that of the FeMnSi based alloy.

Abstract: In this paper, the drawing die of cemented carbide WC-Co (Wolfram Carbide-Cobalt) was taken as the substrate which was preprocessed by Murakami solution and aqua regia. DCS (Direct Current Magnetron Sputtering) was adopted to sputter the Nb interlayer in the bore of the drawing die. By using EACVD (Electron Assisted Chemical Vapor Deposition), micro-nanocomposite coating was deposited. Then, specimens were characterized through methods like SEM (scanning electron microscope) and Raman etc. Results indicated that the drawing die showed very smooth coating surface and a compact, uniform structure; the grain size < 50 nm and surface roughness < 10 nm. It can be inferred from the indentation experiment that there was satisfactory adhesion force between coating and the substrate. So, the drawing die can satisfy the working requirement of drawing wires.

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: 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.

Abstract: The uniform distribution and the stability of the substrate temperature are the most important factors that deeply affect the quality and the growth rate of diamond films. In this paper, cemented carbide cutters were chosen for substrates, the 3D finite element (FE) model of filaments and substrates was developed in ANSYS 8.0, the calculated results show that the substrate temperature is influenced by the filament temperature, filaments diameter, the quantity of the filaments and the distance between the filaments and the substrates. The 3D finite element model of filaments and substrates also provides a basis for selecting the parameters to obtain uniform diamond films in miniature EACVD system.