Advanced Materials Research Vols. 314-316

Abstract: Brush plating has been an important technology for mending the scratched surface of the engineering parts in recent years. The duralumin alloy is common used structural material. The process for brush plating mending of deeply scratched surface of the parts made by LY11 duralumin alloy is introduced, the technologic methods of LY11 duralumin alloy are studied and analyzed, the merits of the brush plating mending technology of LY11 duralumin alloy are discussed in this article.

Abstract: Based on the perspective of the linear expansion coefficient, an anti-oxidation coating on billet heating for silicon steel was prepared. The anti-oxidation coating can be used at 1400oC and it has good property of automatic pelling off, and the oxidation burning loss was decreased by 80.65%. The microstructure of the coating was observed by scanning electron microscope. The results indicate that the high-temperature anti-oxidation mechanism of the coating on the surface of steel billet is cavity clogged by molten slag, and the service life of anti-oxidation coating is relied on the resistance to permeation and erosion of molten slag.

Abstract: The preparation of electrolyte and the technical flow were summarized, the chromium based nanodiamond composite coating was prepared by composite plating process. The metallography structure of plating layer was characterzied, and the hardness, the element of plating layer were tested, the test results and reaction principle were discussed. It was found that the addition of nanodiamond increased the hardness of the coatings. When the concentration of DND in electrolyte is 2.0-3.0g/L,the plating time is about 15-20min, the maximum hardness was obtained.

Abstract: The requirements of the power supply design are proposed based on the principle of discharge process in depositing & welding power supply, and a depositing & welding power system schematic is designed according to the requirements. The control manner of the power supply combines RLC (Resistance-Inductance-Capacitance) circuit with fast SCR, and the deposition and restoration can be achieved by using the NE555 circuit to trigger the fast silicon controlled rectifier. Furthermore, parameters such as voltage, capacitance, frequency, motion mode of electrode are probed into, a depositing & welding test is experimented and the waveform of the power supply are analyzed. According to the results of experiments and analysis, it is clear that the output of the power supply can meet the requirements of working successfully and achieve the required standard to do electrospark depositing and welding operations. However, the actual working electrospark frequency is lower than the trigger pulse frequency added on the fast SCR, which result in a lower efficiency in depositing & welding work. Main reasons for this situation is that the relative movement of the electrode and the work-piece can’ t guarantee the best conditions for electrospark and the fast SCR in circuit can’t be reliably turn-off fast. These research laid foundations for further electrospark depositing & welding power supply design and efficiency improvement.

Abstract: The effect of corona electric field on the surface of Pr-doped ZnTe thin film was studied. The device which can produce the high-voltage corona electric field is developed and used. The V-A characteristics of positive and negative corona discharge between the adjacent needle plates were measured. Whether positive or negative corona discharge, the corona discharge current of the plate is increased with the applied voltage increasing; the voltage range of negative corona discharge is wider than that of the positive corona discharge, meanwhile under the same applied voltage, the negative corona discharge current is bigger, not only its curve is smooth, but also its discharge is stable. The thermal effect of electric field is small. The electric field strength is 7.0 kV•cm-1. By atomic force microscope, it is found that the size of particles becomes large and uniform, and the surface becomes rough with electric field treatment. The measurement results reveal that the average radius of particles is 108.70nm before the effect and 227.27nm after the effect. By UV-Vis Spectrophotometer, it is found that a strong optical absorption peak appears at the region of 220 - 250nm with electric field treatment. This means that the stronger light absorption peak turn out a blue shift under the effect of electric field. The phenomenon of the blue shift proves that the high-voltage corona electric field has an impact on the band gap of the film. The voltage range of the negative corona discharge is wide and stable. The thermal effect produced by the high-voltage corona electric field on the sample is very small, so usually it can be ignored. The high-voltage corona electric field can change the surface morphology of some films, makes the current density of the sample location increase in a small cross section. The negative high-voltage corona discharge should well be used to research in biophysics such as the transgenic plants. High-voltage corona discharge mutagenesis has become a new physical mutation technique. Introduction

Abstract: In this study, the influence of particle type and substrate hardness on the deposition behavior of single WC-17Co particle during the cold spraying process was investigated. The morphology of the deposited particles was examined by scanning electron microscopy (SEM) from the particle surface and cross-sections. It was found that with increasing substrate hardness, the deposition behavior of WC-17Co particles transformed from completely embedding into soft substrate to partially flattening and even rebounding from the hard substrate. In the comparison between different powder types, spherical nanostructured WC-17Co particles experienced the more intensive deformation due to the smaller WC size.

Abstract: Ni–SiC nanocomposite coatings with reinforcing SiC nano-particulates were prepared by electrodeposition on MB8 wrought magnesium alloys. The microstructure, chemical compositions, hardness, corrosion resistance, and wear resistance of resulting composites were investigated respectively. This article details the state of the art in coating technologies, applied to magnesium based substrates for improved corrosion and wear resistance.The experimental results show that, uniform and compact coatings with good corrosion resistance can be obtained on MB8 wrought magnesium alloys. The wear resistance of the coatings were observed to be superior to hard chromium coatings.

Abstract: A sprayed MoB/CoCr cermet coating was formed on 310S stainless steel by low pressure plasma spraying (LPPS), and its durability in the molten Al-12.07wt.%Si has been investigated by SEM、EDS and XRD. The immersion test revealed that the MoB/CoCr coating has much higher durability without dissolution in the molten Al-12.07wt.%Si alloy. Little change of crystal structure, mainly composed of ternary borides of Co2MoB2 and CoMoB, suggesting that the ternary borides have much higher durability.

Abstract: Hard coating can be used as damping treatment. An interfacial damping model, based on the interface slip mechanism, is presented. Interfacial damping ( ) can be expressed as a quadratic function of the interface adhesion strength (N). It means that there exists a suitable bonding strength ( ) which makes the interfacial damping capacity obtain the maximum value. The model can be used to evaluate the damping performance and the interfacial adhesion condition of a hard coating structure.

Abstract: Laser current is a key parameter in laser direct-part marking symbols on a substrate. Different laser current can create enormous impact on bar code contrast, but the influencing regularities are unclear. In this paper, a new significance test method based on the multivariate nonlinear model was proposed to investigate the influencing regularities. First, the multi-element nonlinear stepwise regression model between the laser current, the laser line spacing and symbol contrast was established, and then the model significance test was employed to evaluate the influence between the two factors and symbol contrast. Finally, the influencing regularities were found by comparing the influence between the laser current and the laser line spacing. These regularities are that along with the laser current value increasing the influence of laser current on symbol contrast decreases and that the effect is much smaller and can even be neglected when the laser current reaches or exceeds a certain value. This certain value is 15 A in the Nd:YAG laser Direct-part marking symbols on the aluminum alloy experiments.