Advanced Materials Research Vols. 97-101

Abstract: The Fe32Ni32Si16B18Nb2, Fe31Ni31Si18B18Nb2 and Fe30Ni30Si20B18Nb2, (at. %) alloys are synthesized using low purity of raw materials by high power CO2 laser cladding with synchronous powder feeding. X-ray diffraction results show that the coating has an amorphous structure with some crystalline phases on it. The microstructure of the coatings changes with different amounts of Si. It can be observed that black nanocrystalline grains embedded in the amorphous phase in the TEM image. The coating of Fe31Ni31Si18B18Nb2 alloy was annealed at different temperature for 30 minutes and the microstructure were investigated. The highest Vickers Hardness had exceeded 1300 in the coatings. The amount of Si is a critical factor for fabricating a Fe-Ni based amorphous composite coating.

Abstract: The ZnO films were deposited on quartz glass substrate by RF magnetron sputtering. The ZnO films are highly c-axis oriented with the (002) plane parallel to the substrate. The grains size estimated by the XRD diffraction rises with increase in the Ar/O2 ratio. The optical absorption edge and the near absorption edge characteristics of ZnO films have also been investigated. The optical band gaps of the films have been evaluated from the absorption coefficient of ZnO films. It is found that the value of the optical band gap varys from 3.26 eV to 3.32 eV due to the energy gap enhancement induced by quantum confinement. This variation of band gap can be explained with the theory developed by Brus. For all the films, the absorption coefficient shows the Urbach exponential dependence in the near band edge regime. It is also observed that the value E0 decreases with the Ar/O2 ratio increasing.

Abstract: Laser Surface Texturing (LST) is an advanced method of surface micro-texturing technology. The aim of this paper is to investigate the influence of laser surface texturing distribution patterns on lubricant characteristics for laser texturing surfaces against cylindrical under conditions of film lubrication. The laser texturing surfaces are processed with power levels under YAG laser. Under conditions of constant depth and area coverage ratio of LST,patterns of the texture distribution and the sliding orientation relative to the texture were systematically varied. The experimental results suggested that 20° circumferential interval can increase the load-carrying ability of lubricating film.

Abstract: In friction surfacing process, the temperature field and strain field, especially of coating rod, is considered an important element in analyzing the process’ mechanism and choosing the key process parameters properly. In this paper, the finite element method was employed to simulate the coupling of 3-D temperature field and deformation field of coating rod during friction surfacing. The simulation results show that at the preliminary preheating period, the isotherm goes down at the center part, and the temperature field presents “M” along the radial direction. The temperature increasing rate at the friction interface is higher at first, and then become lower, once the friction system becomes quasi-steady, the temperature here will be stable approximately. The largest effective strain occurs near the center of bottom circle. The simulation results are close to the experimental results, thus builds a basis for analyzing the process’s mechanism, allows for theoretical guidance for analyzing feasibility and helps optimize key parameters.

Abstract: A theoretical model to predict the joint distribution of droplet size and charge density for an electrostatic spray is described based on the maximum entropy method. From known values of the electrostatic spray parameters, the model is used to evaluate the joint distribution of droplet size and charge density for a cone-jet mode electrostatic spray. The predicted results of present model show that it has generally a relatively narrow distribution for both droplet and charge density in a cone-jet mode. Comparatively, the droplet size distribution is narrower than that of the charge density. In addition the two distributions are significantly different in shape. The droplet size distribution is nearly symmetric about its peak position, whilst the left side of the charge density distribution curve is noticeably steeper than the right side. The results are also compared with existing experimental data with agreement considering the uncertainties in the data.

Abstract: Al2O3 ceramic surface was metallized using multi-ionic composite coating technology. The obtained Cu-Ni-Ti composite coating was examined and evaluated by energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffusion (XRD) and sound emissive scratch test (SEST). The composite coating composition, the element distribution, the phase structure of the deposited coating, and the jointing mechanism of the deposited coating/ceramics were analyzed. It was found that the obtained alloy coating layer contained elements such as Cu, Ti, Ni and Fe, etc, and no element segregation was observed. XRD result showed that the diffusion coating alloy layer was composed of CuTi2, Ni[TiO3] and Al2O3. Sound emissive scratch test (SEST) results revealed a good adhesion between the diffusion coating alloy layer and ceramic, and no spallation occurred under the maximum load of 100N.

Abstract: In order to solve the environment problem caused by the inhibitors that are widely used to improve the corrosion and scaling of the carbon steel pipes and equipment in the transportation of the industrial water, the design of using coatings or films on carbon steel is put forward without adding inhibitor. Based on this design, the Ni3P-TiO2 coatings have been prepared on carbon steel by chemical plating and sol–gel method. The coatings mainly compose of Ni3P and TiO2 analyzed by the XRD patterns. The microstructure and morphology of the Ni3P-TiO2 coatings are full, smooth and no cracks using a scanning electron microscopy. The properties of the Ni3P-TiO2 coatings are determined through the electrochemical experiment, scaling inhibition and antibiosis experiment. The results demonstrate that the coatings have the excellent properties of anticorrosion, scaling inhibition and antibiosis. The mechanism of the efficiency maybe due to the change of the interfacial energy, but it need prove through the farther examination.

Abstract: The structure and properties of H13 steel treated by the QPQ Salt-bath treatment with different content of Rare Earth (RE) LaCO3 were studied. The surface of H13 steel was treated using this method. The microstructure and depth of the treated surface for the steel were analyzed using SEM. The sliding wear resistance was tested on the M-2000 tester and the micro-hardness was tested using 401MVA microscopy hardness tester. The results showed that the thickness and the wear resistance and the speed of nitriding was highly improved and the performance of nitriding layer and the nitriding structure was improved.

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: Micro-arc oxidation (MAO) is an effective approach to improve the properties of aluminium and its alloys by forming ceramic coatings on the surface. However, the oxide layers often have a porous surface structure, which limits their mechanical properties. In order to enhance the properties of the layers produced by micro-arc oxidation, SiO2 nanoparticles reinforced Al2O3 composite coatings were produced on 7A52 aluminium alloy by adding SiO2 nanoparticles into the electrolyte. With the addition of SiO2 nanoparticles in the electrolyte, the formation rate of Al2O3 coating enhanced considerably and the current density through the sample surface became much higher than that without SiO2 at the same voltage. The coatings were investigated with X-ray fluorescence spectrometry (XRF), Scanning electron microscopy (SEM), Vickers hardness test, and reciprocating friction and wear test. Compared with the Al2O3 coatings without SiO2 nanoparticles, the n-SiO2 reinforced Al2O3 composite coatings are much denser and harder, and the wear resistance is also improved significantly. The improvement can be attributed to the enhancement of the surface structure and morphology of the n- SiO2 reinforced Al2O3 composite coatings.