Advanced Materials Research Vols. 591-593

Abstract: Basis on a series of investigation and study, the rotation speed of helmet, the moving speed of spraying gun and spraying angle are of greater impact on the final spraying qualities than others. The spraying process of helmet is simulated with UG NX. After analysis for the spraying trajectories, the optimal speed of the helmet rotation and spraying gun movement are obtained. There are several coating thickness deposition model with a wide range of applications, such as the Gaussian model, finite range model, and β distribution model. Using MATLAB to test the path of the spraying, according to the simulation and adjusting the speed of helmet's rotation and gun's movement, the desired spraying result has achieved. In addition, users can know the approximate results before spraying.

Abstract: Plasma nitriding technology was carried out on the surface of bearing steels. The phase composition and microhardness of the nitrided layer were analyzed. Sliding wear characteristics of the nitriding steel were studied on an Optimol SRV IV oscillating friction and wear tester at room temperature. The fretting wear mechanism was investigated with scanning electron microscopy (SEM) and 3D surface profiler. The results showed that Cr2N, Fe4N, Fe2 ~ 3N phases were observed on the nitrided surface layers; lubricating condition, normal load and friction velocity have great effect on the friction and wear characteristics of the plasma nitrided steels.

Abstract: To fabricate high aspect ratio micro/nano features, demolding is more challenging than filling of melt into micro mold as solidified micro features can be easily peeled off when demolding resistance is high. Besides using anti-stick agent, using deformable mold is a new solution proposed by the authors. This paper presents a setup for testing the deformable active mold. Experimental results on micro thermal molding with the developed mold deforming system prove that the new system can successfully demold high aspect ratio micro features that can not be produced with traditional metal mold.

Abstract: To meet different electrical or optical functionalities, thin films are often of multiple layers processed at high temperatures. Substantial residual stresses can therefore develop in such thin film systems due to the disparate thermal properties of the individual material layers. High stresses can lead to mechanical failure of the systems and thus understanding the residual stresses in thin film systems is important. This paper presents a systematic way to characterize the residual stresses in epitaxial, polycrystalline and amorphous layers by using X-ray diffraction (XRD) techniques. The single-point XRD pattern renders the stresses of crystalline layers and the scanning XRD gives the curvature of the whole film. Based on the newly-developed analytical model, the residual stresses of each layer can all be determined.

Abstract: The laser cladding is used on the surface of 4Cr14Ni14NW2Mo heat-resisting steel, In the laser cladding added 0. 5% CeO2,Ni-based WC coating can be formed. The effects of rare-earth oxide CeO2 on the microstructure and microhardness and wear-resistance and corrosion-resistance of Ni-based metal-ceramic coatings are investigated. Observing and analying the microstructure, Measuring microhardness, Checking the dry friction and wear properties of high-temperature of the coating in different temperature. The results showed that the microstructure of Ni21+20%Wc+0.5%CeO2 cladding layer is even small, Hardness is more uniform and gentle. Wear mechanism of the laser cladding layer changes with temperature changes.Abrasion is the main mode under Low temperature , it was transformed into Adhesive wear and Oxidation wear along with the increase of the temperature.dry friction and wear properties of high-temperature is excellent.

Abstract: Micro overmolding is becoming more important with the rapid development and applications of microproducts in bioengineering, electronics and other areas in recent years. This paper presents our findings in studying polymer interfaces in micro channels of a micro mold during overmolding process. The bonding strengths between polycarbonate (PC) and thermoplastic polyurethanes (TPU) were examined and compared under different overmolding conditions. Results show bonding behaviors in micro channels are not only affected by temperatures, they are also influenced by surface roughness.

Abstract: This paper studies the impacts on the particle size and shape of silica sands by roasting times and different methods of cooling, which finds out that different methods of cooling may lead to different cooling rates of sands; that is, adopt water-cooled fluidized bed to cool down sands, the cooling rate is the highest; the secondary is by cooling cylinder, and common fluidized bed leads to the lowest cooling rate. After being roasted and cooled, no matter which method is adopted, the sands are not changed obviously in particle size and shape, which indicates that roasting times, different cooling methods and cooling rates have no obvious impacts on the particle size and shape of silica sands.

Abstract: The 2Cr13 axle sleeve, used in N52 water pumps, suffered wear after being tested for a relatively short time and fractured when it was beat under the dynamic load. Optical metallographic microscopy, scanning electron microscopy (SEM) and Vickers hardness tester for the fractured 2Cr13 axle sleeve were used to determine the most probable causes of the failure. The results showed that the failure was mainly due to the inappropriate technological parameters of high frequency induction heating and a large amplitude rotor vibration. Meantime, cracks were easily found not only close to the frayed surface but also in the inner part contributed to the inappropriate parameters. Finally, the proper protections were advised to be used for preventing this type of failure for the axle sleeve from happening again in the further.

Abstract: A finite element model was established to describe the flow field and temperature field during the surface modification by electron beam in this paper. The driving forces of molten pool were considered in the mode. The flow of liquid metal was different between the inside and outside of the beam spot; the direction of the flow was along the surface to the specimen thickness. When the liquid metal was in the bottom of the pool, it flowed along the bottom to the pool edge. The largest flow velocity was 0.28m/s in the center of the beam spot, the minimum flow velocity was 0.11 m/s in the bottom of molten pool. The temperature of sample is uniform distribution, the temperature distribution show a gradient distribution in cross section.

Abstract: The phase stability and site preference of transition metal carbides Cr in Fe7-xCrxC3 are studied based on the pair potentials obtained by the lattice inversion method. The lattice constants and cohesive energy of Fe7-xCrxC3 with the content x are calculated. The results show that Cr atoms substitute for Fe with a strong preference for the 6c1 sites and the order of site preference is 6c1, 6c2 and 2b. Calculated lattice parameters are in good agreement with the experimental data. Moreover, the total and partial phonon densities of states are first evaluated for the Fe7-xCrxC3 compounds with the hexagonal structure. We also provide some information on the vibrational properties of transition metal carbides, such as the specific heat and Debye temperature were also evaluated.