Advanced Materials Research Vols. 314-316

Abstract: In this paper, the effect of particle concentration and magnetic field on the tribological behavior of magneto-rheological (MR) fluid is investigated using a pin-on-disc tribometer. The wear loss and friction coefficient are measured to study the friction and wear properties of MR fluid. The morphology of the worn pin is also observed by scanning electron microscope (SEM) in order to analyze the wear mechanism. The results obtained in this work show that the wear loss and friction coefficient decrease with increasing particle concentration under the magnetic field. Furthermore, it is demonstrated that the magnetic field has a significant effect on improving tribological properties of MR fluid, especially the one with high particle concentration. The predominant wear mechanism of the MR fluid has been identified as abrasive wear.

Abstract: Composite membranes of TiN, WC/C and TiAlN+WC are successfully prepared by means of magnetron sputtering. An analysis of the membranes’ hardness, surface topography and chemical composition indicates that the composite membrane have a greater hardness, and are compact in structure and uniform in texture. A abrasion test is conducted by applying the three membranes respectively to tricone bit bearings, and then a comparison made between them and non-membrane tricone bit bearing leads to the finding that tricone bit bearing with TiAlN+WC/C composite membrane has the highest abrasion resistance, with a dramatic increase of 30%~40%.

Abstract: Special V-shaped heat bending test was designed for 22MnB5 hot forming steel of different thicknesses. Blanks after heating 5 min at around 950°C to austenize fully were bended at different temperature conditions, and simultaneously the spring-back behavior and microstructure features of heat bending specimens were investigated. The result shows that 600-650°C temperature zone is optimal for bending forming and martensite texture transforming. Real hot forming anti-collision beams were produced at 600-650°C and comparison bending test was conducted to reveal more qualified mechanics at this temperature zone.

Abstract: Cold spray is a new surface engineering technology. In this paper, pure copper particles were sprayed on the Al substrate by this method and the copper coating was deposited sucessfully on the surface of the substrate. The microstructure of the coating and the interface between the coating and the substrate were observed by optical and scanning electron microscopes, and the phase was identified by XRD for the pure copper particles and the coating. The microhardness of the coating is measured. The results show that mechanical bonding is the main mechanism for the interface between the coating and the substrate, and there is a few metallurgical bonding for the interface; the coating is dense and its porosity is less than 0.4%; XRD results indicate that there is no oxidation occurred during the spray process. The microhardness of the coating is about 160Hv, which is higher than that of the as-casted copper.

Abstract: The Tribological properties of FeCrNi/CBN composite coating with spraying high velocity arc is studied. Images and components and cross-section microstructure of coatings are analyzed by the means of SEM, and EDS etc. This research indicates that FeCrNi/CBN composite coatings have typical layered structure characteristic and high bond strength and hardness. Friction coefficient of coatings at room and high temperatures have “Run-up” period. With the increase of temperature, friction coefficient of coatings becomes low and wearing capacity of coatings becomes high. The adding of CBN powder highly improved the wearing capacity of coatings.

Abstract: Simulations of the supersonic flow field inside and outside of the Laval nozzle with single hole and nine holes were carried out based on the computational fluid dynamics method. The effects of different standoff distance and particle diameter on impact velocity of Cu particle spraying from single hole and nine holes were investigated firstly. The results show that the particle velocity obtained with the nine holes nozzle is higher than that of the single hole nozzle under the same standoff distance, and the smaller the standoff distance, the higher the particle velocity may be obtained with the nine holes, and the higher particle velocity may be obtained with smaller particle diameter for particles with diameters of 1 ~ 15 μm. Furthermore the effects of different spraying pressure and temperature on particle velocity of Cu particle spraying from the nine holes nozzle were also studied. And the simulations indicate that the higher the spraying pressure and temperature may make the particle spraying with greater velocity.

Abstract: An acrylate emulsion was modified by vinyltriethoxy silane (VTES, trade name A-151) to synthesize the acrylosilane emulsion with high properties. The effect of the amount of A-151 on the properties pf the emulsion was investigated. It found that adding 6 % of A-151, the fraction extensibility of the emulsion film could be increased to 530 % and its water absorption was reduced to 4.2 % while adding 10 % of A-151. On the other side, the particle size and distribution of the emulsion were analyzed by Scanning Electron Microscopy (SEM) and Malvern Particle Size Analyzer (PSA) respectively. The measuring results showed that the particle diameter of the modified emulsion could be between 100 and 700 nanometers, and the properties of the emulsion could be apparently improved by adding A-151 into the system of emulsion polymerization.

Abstract: The application of Taquchi method in the optimization of PTA hardfacing process for the wear-resistant plate has been studied in this paper. The operation current, powder feeding rate, torch moving rate and torch moving distance are the four factors evaluated in this research. Taguchi methodology is applied to make the association of these factors in optimization and through the observation of microstructure, hardness, wear-resistance and dilution rate to evaluate the effects of these factors on the hardfacing layer of the wear-resistant plate. By the microstructure observation, the more sturdy and compact of the Cr-C dendrite structure, the better the hardness and wear-resistance of the hardfacing layer is. The torch moving distance is the major factor of the surface hardness, and the torch moving rate for the wear, the working current for the dilution rate.

Abstract: A novel processing way for the continuous helicoid reflective mirrors is proposed. We use an intelligent oven to accurately control the glass temperature and successfully produce a helicoid reflective mirror in B270 glass. Then we test the shape and optical properties of the helicod reflective mirror via the three-coordinate instrument measuring and interference experiment.

Abstract: To improve wear resistance and service life of boron cast iron cylinder, plasma beam hardening on surface is adopted.Scanning electron microscope,X-ray diffractometer and micro-hardness tester is used to analyze the effect of working current on the structure and properties of plasma beam hardening layer at the junction of the hardening traces. The results show that the microstructure of hardening layer at the junction is hidden acicular martensite, retained austenite and flake graphite. With the increase of working current, the content of retained austenite decreases, the hardness and depth of the hardening layer increases. The highest hardness is not achieved at the surface of hardening layer but at the second-surface layer which has a certain distance to the surface. The uneven distribution of hardness in hardening layer leads to large gradient at the both sides of the highest hardness and the gradient decreases with the increase of working current.