Dong Bo Wei

Design of Scanning Micro-Arc Oxidation Forming Ceramic Coatings on 2024 Aluminium Alloy

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.

Forming Ceramic Coating on Al2024 by Scanning Micro-Arc Oxidation

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.

Tacho Plate’s Technological Procedure Compilation and the Fixture’s Digital Design

Tacho plate is a common speed regulation mechanism in automobile, but because of its complex structure, high precision, there has been no ideal processing method. Based on the Pro.E, this paper compiles the processing technic of the Tacho plate which combining with the practical situation and comprehensive considering the precision, economy, efficiency, roughness, lifetime and other factors, and digital design a specific work fixture regarding one of the most important procedure. Eventually it achieves a very satisfactory result. First of all, understand the working condition of Tacho plate through on-the-spot investigation, reviewing the literature and some other methods, and then preliminary analyze the processing technic of Tacho plate. Secondly, constantly improve the processing technic of Tacho plate through in-depth analysis of the actual situation and comprehensive considering the machining precision, economic benefit, efficiency and some other aspects to make the best processing procedures. Furthermore, make in-depth analysis for the fixture of drilling Φ10 hole. Considering the machining accuracy, use the ganged clamping mechanism with the support plate, regulative support nail, and rhombic pin for joint locating to meet the requirements to the greatest extent. Finally, use the Pro.E software for three-dimension model and further verify the fixture plan designed before through this digital design.

Research of MEDM Pulse Power Based on the Non-Resonant Natural Oscillation

Aiming to discharge feebly, improving the frequency of MEDM power pulse is an ideal choice. But due to the influence of power resistor, capacitor, inductor with stray capacitance and stray inductance, increasing the higher pulse power frequency met bottleneck. Through the analysis of MEDM discharging circuit and routes, this paper puts forward the theory of not using components, but depending on the natural oscillation of MEDM machine tools and connection line to make MEDM pulse power. Through theoretical calculation and simulation, the oscillation period of discharging circuit can be controlled in 1.5ns, and the pulse width can be less than 750 Ps. It provides theoretical support for making picosecond pulse power and nanometer manufacturing with MEDM.

Study on Stray Capacitance of MEDM Machine Tool

The stray capacitance in the process of MEDM has been the key problem of influencing the processing dimension and precision. This paper puts forward a method of measuring the stray capacitance of MEDM machine tool, through recording the charging waveform of two cases that the RC pulse power is on the machine tool or not by an oscilloscope, and then the measured data are substituted for the capacitance charging formula, we get the stray capacitance value of MEDM machine tool. This paper also tests the cases of different charging voltage and different tool-electrode length, finally we find that the tool-electrode length has a big influence on the stray capacitance.

Study of the Effect of Electric Field Distribution to the Pulse Electrochemical Machining

This paper studies the electrochemical machining on the surface of nickel-based alloys with a tubular electrode and analyses the effect of electric field distribution and current distribution to the shape of concave holes during the processing. It is concluded that the maximum distance between the positive and negative poles in the reaction of electrochemical machining. It is analyzed that order of electrochemical machining surface holes in the direction of hole radius and hole depth and the variation laws of reaction speed.

On the Deep Small Hole Machining Method of Nickel-Based High-Temperature Alloy

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.

Influence of the Processing Parameters on the Coating Hardness on LD10 A-Alloy

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.

Experimental Study of Kerf Machined by Micro-WEDM

In Micro Wire Electrical Discharge Machining (Micro-WEDM), the kerf width varies with different machining parameters, which will greatly influence the machining precision. In order to study the kerf variations in Micro-WEDM, the influence of kerf variation is analyzed and the experiment considering the kerf width and machining speed are performed on self-developed micro-WEDM under different machining parameters. With the reference of the experiment results, 32μm wide slot is machined with Φ30μm wire-tool on stainless steel workpiece.

Narrow Beam Machining on Micro-WEDM

This paper aims to investigate the performance of narrow beam machined by MWEDM. The narrow beam machining experiments are carried out on self-development Micro-WEDM with Φ30μm electrode wire. Narrow beams with the width around 10μm are machined on E52100 steel under different machine conditions (discharge energy, servo reference voltage). Based on the analysis of the experiments results, the coupled temperature and stress analysis using ANSYS finite element analysis software is performed to investigate causes of the failures on process.