Papers by Author: Shi Chun Di

Abstract: This paper applied the micro-arc oxidation technology to TIG weld joint based on titanium alloy. The optical microscope, SEM, XRD and polarization curve were used to analyze the joints metallographic phase, the coating morphology, the phase composition and corrosion resistance. Research results showed that the grain was grew gradually coarser from base metal to joint. The joint surface obtained a uniform morphology after micro-arc oxidation. The joint and base metal was made up of α-Ti and their coatings are mainly composed by rutile-TiO₂. The surface morphology and phase composition are similar after micro-arc oxidation. Polarization curve tests demonstrated that the corrosion potential performance of the coating was enhanced by micro-arc oxidation.

Abstract: The present work investigated the effect of laser surface melting (LSM) process on micro arc oxidation (MAO) coating prepared in silicate electrolytes (Si-MAO) and aluminate electrolytes (Al-MAO). Plasma intensity of laser spots, element content and phase constituents of coatings were analyzed. During LSM remelting process, the formation of heat sources and micro molten pools on the surface of MAO coating were discussed. The results showed that the moderate plasma was formed more easily on the Si-MAO than Al-MAO coating, owing to the temperature threshold of melting oxide layer was decreased for silicon-containing MAO coating during LSM treatment. Besides, the Si-MAO coating of laser-treated had low porosity and smooth surface.

Abstract: Formation mechanism of the micro-arc oxidation spark discharge is always a research problem; so far there isnt a theoretical model for analyzing the spark discharge formation which is widely recognized. Based on analyzing the reaction phenomena and the coating feature in the different periods of the red spark discharge, the formation model of the red spark discharge was established. The spark discharge formation mechanism is shown that it causes the spark discharge formation that the electron bombards the gas layer wrapping the coating in the infancy of red spark discharge stage; at the later period the area of strong electric field generates the spark discharge where the coating of excessive polarization turns out easily.

Abstract: In this paper, a machining method of deep hole on the nickel-based high-temperature alloy using the pulse electrochemical machining is proposed. The effect of five technological parameters on the depth-averaged radial overcut of the hole to be machined in the machining process is discussed; then the mathematical model is built, and the effect of parameters on the overcut is illustrated. The speed ratio is determined to judge the quality and the processing performance of holes. The technological parameters adopted in the experiment, can be used to produce effectively high-quality hole of big proportion of depth to diameter on the nickel-based high-temperature alloy in the machining process.

Abstract: Micro-arc oxidation (MAO), also called plasma electrolytic oxidation (PEO), anodic spark deposition (ASD), or micro-arc discharge oxidizing (MDO), is an effective surface treatment technique which come from anodic oxidation technology. Via increasing the anodic voltage breaking through faraday area to a high stage accompanied by micro-arc discharge phenomenon, It indicated the ceramic coatings thickness increase along with the scanning times increase, while the thickness increment reduces. The phase composition, morphology and element distribution was studied by X-ray diffraction, scanning electron microscopy and line scanning. The morphology of the ceramic coatings shows it divided into compact layer and loose layer. And it composes of α-Al₂O₃ and γ-Al₂O₃.

Abstract: A medicinal titanium alloy hydroxyapatite coating was fabricated by microarc oxidation process, and a kind standard of simulated body fluid was configured, after that the biocompatibility experiment was carried out. The soaked coatings surface morphologies were observed and analysed by scanning electron microscopy,and the coating spectra were simultaneityly researched by X-ray diffraction. The instance of degradation and precipitate were investigated,and the transformation of Ca/P value were measured.

Abstract: The method of machining deep hole on Ni-base alloy which can tolerant high temperature by pulse electrochemical machining has been proposed in this paper. Five technical parameters are discussed on the effect of mass removal rate of machining process. Establish a dynamic math model, and analyze the effect of process parameters on the mass material removal rate of deep small holes. Machining accuracy of deep small holes was analyzed.

Abstract: With the development of micro arc oxidation and the growing maturity of the industrialization, the electrolyte service life and stability attract more and more people. In this paper, the electrolyte service life was researched. Under the same technological conditions, it was found that the critical factors affecting the electrolyte service life are the single-processing area and the electrolyte volume. With prolonging the working time of the electrolyte, the gel deposition mass in the electrolyte and the initial voltage always change. The experiment indicates that the electrolyte service life will assume the curve extension when reducing the single-processing area or increasing the solution volume. To some extent, the initial voltage and gel deposition can indicate the active state of the electrolyte, and can be considered as the sign whether the electrolyte service life becomes due.

Abstract: Micro-arc oxidation (MAO) is a novel technique to deposit ceramic coatings on the surface of valve metals such as Al, Mg, Ti and their alloys. The oxide films prepared by this technique have a dense structure, high adhesion and excellent integrated mechanical properties. This technique is especially suitable for the surface treatment of machine parts that work at high speed and have a higher demand for resistance to wear and corrosion. There have been many studies in this field in the last few years. The development of micro-arc oxidation and its applications in industrial field was reviewed. Based on conventional micro-arc oxidation, an innovative scanning micro-arc oxidation technology with visible advantages was developed in this paper. Moreover, verification experiment on scanning micro-arc oxidation was carried out, and the experimental results suggested that scanning micro-arc oxidation could be conduced at a high efficiency but low cost way. At last, the effects of scanning times on film thickness were discussed.

Abstract: The paper discusses the influence of processing parameters on the hardness of LD10 aluminum alloy coating treated by the power source with positive and negative pulse in the alkaline electrolyte. Lots of experiments were done with different processing parameters including positive current density, negative current density, frequency, duty ratio, processing time and electrolyte temperature, and the micro-hardness tester HVS-1000 was used to measure the coating hardness. The results indicate that elevating the duty ratio, or reducing the frequency can be advantageous to improve the coating hardness, and the coating is the hardest treated in electrolyte at the 30°C. And when the value of the positive and negative current density is reasonable, and the processing time rationally matches with the current density, the coating with HV2800 can be obtained.