A simple and effective surface coating technique, electro spark deposition (ESD), has been used to produce WC coatings onto H13 steel surface. Influence of process parameter (output voltage, output capacitance, discharge frequency, specific deposition time at el) on the coating thickness was studied. It can be seen, choose output voltage 80V, output capacitance180 μF, discharge frequency 2000 Hz, specific deposition time 8min/cm2 obtained to optimal overall quality of coating. The morphology and microstructure of coatings were analyzed using scanning electron microscopy (SEM). The WC coating had an average thickness of about 60 μm and formed metallurgical bonding with the substrate.
Nano material is a new type of multi-functional materials, this article simply introduces the development present situation, performance and preparation method, and application in the aerospace field.
Electro-spark deposition (ESD) is a microwelding process that utilizes short duration of electrical pulses to deposit electrode materials to a metallic substrate. In this paper, taking TA2 bar as electrode, a deposition layer of thickness up to 40μm was built up to on 7075 aluminum alloy substrate by means of ESD. The deposition layer is metallurgical bonded to the substrate. The microstructure, phase composition, and micro-hardness of TA2 coating were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and micro-hardness test. The microstructure of the coating was mainly composed of TiN phase, Al3Ti phase, AlN phase and Al phase. Its micro-hardness reached 295 HV0.05, about 2 times as high as that of the substrate. The hardness at the cross-section of the entire deposition layer showed a gradient distribution.
The injection molding process of plastic parts is simulated and analyzed through a three-dimensional model of bottom cover of USB (Universal Serial Bus) extender obtained by Pro/E software and MPI module of Moldflow software. Orthogonal test is applied to analyze the influence of press time, press pressure, mold temperature and melt temperature on the warpage of plastic parts. Those being influenced by factors above are listed in order as press pressure, melt tempreture, mold tempreture and press time. The optimum parameters are obtained by analyzing effect trend that the four factors can influence on warpage.
Constantly use combined tubing string to meet the strengths requirement during oil production and worover job. The maximum setting depth of combination tubing string is relevant to well deviation, casing program, fluid level, as well as tubings material, size, collapsing strength, internal-outer pressure resistance and floatage of holebore fluid. Based on mechanics analysis and mathematical development, obtained mathematical relation which can meet requirement of different combined tubing string, and described relation of conventional tubing string composition length, it can be used for tubing string strengths checking.
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