Papers by Author: Yin Hui Huang

Abstract: The formation of cracks is one of the key problems which restricts the development and application of laser-clad ceramic coating technique on metal surface, especially during laser multi-layer cladding process because of stress superposition effect. In this study, a thick ceramic coating was fabricated by laser multi-layer cladding based on series of crack control methods. The crack of clad layer was controlled by preheating and slow cooling rate of sample with incubator, applying the ultrasonic vibration and adopting closed-loop controlling temperature of molten pool during laser cladding process. In addition, the crack of layer was controlled by the strengthening and toughening effect of remained nanoparticles in the laser-clad coating. Moreover, the use of a transition layer is also help to reduce layer cracks. The results show that the laser-clad ceramic coating is free of macroscopic cracks and the mcirocrack density is significantly reduced.

Abstract: In this study, thick ceramic coatings were fabricated by laser multi-layer cladding with Al₂O₃-13%TiO₂ nanostructured agglomerated powders based on series of crack control of clad layer. The microstructural characteristics and microhardness of the coating were investigated by using scanning electron microscopy (SEM) and microhardness measurement. The results show that the laser-clad thick ceramic coating has no obvious interface between the layers with dense, continuous structure, and almost no pores and free of large penetrating cracks. The ceramic layer is composed of fully melted regions (fine equiaxed grains) and partially melted regions (remained nanoparticles). In addition, the most microcracks in the coating are focus on the partially melted region. The grain size of ceramic coating in the depth direction is gradually increased, while the hardness along depth direction is gradually decreased.

Abstract: Laminated templates electro-deposition (LTE) is a new manufacturing technique aimed at a highly precise and low-cost fabrication of metallic structures through a number of planar template-patterned depositing. The ability to control deposit surface non-uniformity in each planar depositing has been proved a key to this technique. Correspondingly a 3D simulation for electrical field has been modeled using finite-element method in line with the real experimental conditions. The mapped contour of simulating proved the variedly distributed electrical field and basically match with experimental results. Three groups of LTE test by direct current, pulse and double-pulse current are introduced and assessed in term of their effect to improve uniformity. By comparison, pulse application, especially double-pulse offered a better deposit quality with optimized parameters including pulse width, frequency, working time and off time. A bulk of 10-15layers copper parts, section size 20mm×20mm and 4-6mm thick were produced using the modified parameters.

Abstract: Involute helical gears mesh based on the intersections of involute helicoids. However, spiral involutes on the tooth surface do not participate in meshing directly. A new type of gear drive, the spiral involute gear drive is proposed that works on contact of spiral involutes. The generation of tooth profile is introduced in detail. Through relative-stagnation method spiral involutes prove to have conjugation characteristics. To testify whether the transmission ratio of cylindrical spiral involute gears is constant, simulation is implemented in commercial codes ADAMS based on solid models of a pair of spiral involute gears. The computed results show that this novel gear drive can achieve a constant transmission ratio. Due to transmission with uniform velocity, cylindrical spiral involute gears can be used in transmission between intersecting axes, so that generating milling and generating grinding can be achieved.

Abstract: The system components and the theory of jet electrodeposition orientated by rapid prototyping (RP) are introduced.The nanocrystalline copper parts with simple shape were fabricated by RP technology. The microstructure evolution of the nanocrystalline Copper layer was examined by means of the Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). The results show that the jet electrodeposition can greatly enhance the limited current density, fine crystalline particles and improve deposition quality. The copper deposited layers have nanocrystalline microstructure with average size of 55.6nm. The grain size decreases to 41.4 nm in crystal plane (311).

Abstract: A jet electrodeposition device was carried out to prepare Cu-Al₂O₃ nanocomposite coatings. The influence of the concentration of Al₂O₃ in the electrolyte and the parameters on the content of the Al₂O₃ in the deposit was investigated. The coatings ingredient and microstructure was measured by the scanning electron microscope, the microhardness tests were conducted on an microhardness tester. The results show that the copper deposited layers have nanocrystalline microstructure with grain size of about 50nm . The amount of Al₂O₃ in composites first increased and then decreased with an increase in the concentration of Al₂O₃, current density, temperature and jet velocity. The composite with optimum atomic percent of Al₂O₃ (14.4 at%) can be obtained at the concentration of 30 g/l , cathodic current densities 300 A/dm2, temperature 30°C, and jet velocity 8 m/s . The addition of Al₂O₃ in copper increases the microhardness of the electrodeposited coatings.

Abstract: The principles of jet electrodeposition orientated by rapid prototyping were introduced. The nanocrystalline nickel parts with simple shape were fabricated using jet electrodeposition. The microstructure and phase transformation of nanocrystalline nickel were observed under the scanning microscope and X-ray diffraction instrument. The results show that the jet electrodeposition can greatly enhance the limited current density, fine crystalline particles and improve deposition quality. The nickel parts prepared by jet electrodeposition own a fine-grained structure (average grain size 25.6nm) with a smooth surface and high dimensional accuracy under the optimum processing parameters.