Key Engineering Materials Vols. 373-374

Abstract: In order to control surface microscopic quality of sheet metal after laser peen forming (LPF), visual numerical analyses for SUS304 plate was employed. Based on the FEM code ABAQUS/CAE, a conversion model of laser shock wave loading was established. The tracks controlling technology of LPF was solved by functional element programs. The micro-plastic flow process of surface material was analyzed, and the change of residual stress distribution as well as micro-topography in real time can be shown with the movement of pulsed laser beam. On the basis of FEM simulation, LPF experiments were carried out. The micro-topography and section analysis were analyzed by AFM, surface residual stress was measured by X-ray diffraction method. It was found that after LPF, the surface irregularity was less than 0.15μm, the variation of average surface roughness was slight, both sides of deformed sheet existed useful residual compressive stress, and the maximum stress was -616.1MPa, meanwhile average surface micro-hardness in the peened zone was higher than the base’s surface. Simulative results show a good agreement with experimental results.

Abstract: Surface of gear that works continuously tends to be wore. Hardfacing on worn gear can repair its worn surface, restore its precision, consolidate its surface property, and save cost. Micro-Plasma Arc Welding (micro-PAW) has low heat input and narrow heat-affected zone, and it has good properties of energy concentration and high energy density. Therefore, hardfacing by micro-PAW is an effective method to repair worn gear surface. KF-Ni60A Ni-based alloy powder has good weldability property, and KF-Ni60A welding layer has low friction coefficient and good property of wear resistance between metallic hard surface, so it is a kind of good overlaying material that can be applied to the welding process to repair the worn gear surface. In this research, the method of overlaying on worn gear using KF-Ni60A Ni-based alloy powder by micro-PAW is studied. The microstructure of deposition layer and the elementary distribution of cross-section are analyzed, the surface hardness and wear resistant property of the layer are measured. The result indicates that the deposition layer and the base metal bond well, the layer has high adhesive strength and hardness, low porosity, and good property of wear resistance.

Abstract: Ti ion and C ion is implanted into AZ31 magnesium alloy surface by metal vapor vacuum arc (MEVVA) implanter operating with a modified cathode. This metal arc ion source has a broad beam and high current capabilities. Implantation energy is fixed at 45K eV and dose is 9×1017 cm-2 and 3×1017 cm-2 respectively. Through ion implantation, Ti ion implantation layer approximately 1000nm thick is directly formed on the surface of AZ31 magnesium alloy, by which its surface property is greatly improved. Microstructure, the component distribution and phase composition are analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The property of hardness of the ion implantation layer was studied by HMV-1T Vickers micro hardness tester. The results show that Ti ion implantation layer of a magnesium alloy surface is mainly composed of TiO2, MgO and a little of TiO. The Ti-C double ions implantation layer is composed of MgO, TiC. The hardness of ion implantation layer is improved.

Abstract: The Ag nanoparticles colloid was prepared by pulsed laser ablation for different time in 10 ml distilled water without any surface active agent, and it was analysed by means of UV-visible spectrophotometer and transmission electron microscopy (TEM). The results showed that the ablation efficiency and absorbance increased fast and shift to higher energies with increasing ablation time from 5 to 10 min, then increased slowly from 10 to 20 min, and increased fast again from 20 to 25 min. The morphologies of most Ag nanoparticles were nearly spherical. The average diameter and its distribution decreased from 5 to 7.5 min, then increased from 7.5 to 15 min, and decreased from 15 to 25 min.

Abstract: Silicone rubber (SIR) samples are exposed to CF4 capacitively coupled plasma (CCP) and inductively coupled plasma (ICP) at radio frequency (RF) power of 60–200 W for a treatment time up to 20 min, respectively. Static contact angle is employed to estimate the change of hydrophobicity of the silicone rubber modified by the two coupled types of CF4 RF plasma. A milder enlargement of static contact angle of SIR samples modified by ICP treatment is observed compared with that by CCP treatment. The hydrophobicity of the modified SIR surface by CCP treatment increases to a maximum, and further decreases toward the hydropholicity. The higher self-bias on the SIR samples being modified by CCP treatment than that by ICP treatment leads to the more dramatic physical and/or chemical reaction on the SIR surface, resulting in the competition between fluorination and ablation or etching.

Abstract: To achieve sustainable development and to solve the question of resource recycling and environment protection, green remanufacturing should be considered in the life cycle of the used railway rolling-stock components. These invalidated components resulting from fatigue and wear, such as coupler, could be remanufactured using laser surface hardening technology as the key processing. The objective was to harden the coupler backend pinhole interface, and to repair the layer with wear and fatigue crack on the wall of pinhole. Laser transformation hardening and laser melt-solidification hardening was used to the new manufacturing process to improve wear resistance of the surface of coupler backend pinhole. Laser surface cladding was used to repair lost material area for the reason of wear or fatigue, in order to offset the geometry size and satisfy the assembly relationship, and to increase the strength, the hardness and the wear resistance of the substrate. To the E class steel, typical coupler metal, the related laser process variables and materials were test and optimized. For the sake of verification these tests, related hardening area mechanical behaviors examinations including hardness, wear resistance, impact resistance and metallographic examinations were given. The result of the examinations show that the laser hardening area joins with the substrate being metallurgic join, and the behaviors examined were equal or best than the substrate. These means that laser surface hardening technology could be applied to the green remanufacturing of railway couplers as key processing.

Abstract: High-intensity pulsed ion beam (HIPIB) irradiation at 300 A/cm2 with a shot number of 1, and 5 was performed on the coatings and caused the modification of properties. Porosity and rough surface of EB-PVD (Electron Beam-Physical Vapor Deposition) deposited ZrO2-7%Y2O3 coatings with the thickness of 150 μm on heat-resistant steel have been characterized using the ultrasonic reflection coefficient phase spectrum. With increasing the shot number, the surface remelting and ablating filled gaps and caves between columns, and induced more uniform and compact structure. The ultrasonic measurement was investigated using immersion focusing pulse echo method with a 10 MHz transducer. The ultrasonic reflection coefficient related to frequency, velocity and attenuation coefficient were analyzed based on the acoustic transmission model in a multi-layered structure. For the as-deposited coating and coatings irradiated by HIPIB with the shot number of 1 and 5, the ultrasonic velocity changed from 2950 to 3170, and 3255 m/s respectively. The relationship between the attenuation coefficient and the frequency has been deduced based on the numerical fitting of the phase spectrum. The corresponded expressions are 1.35 α = 0.105 f , 1.2 α = 0.045 f and 1.14 α = 0.035 f , which displays that the attenuation coefficient decreases with the increasing of shot number. The ultrasonic results are in agreement with SEM observations, which have indicated that the coatings became denser and uniform with increasing the shot number. From the velocity and attenuation coefficient, the density, porosity, and microcracks of the coatings can be nondestructively evaluated utilizing the method of this paper.

Abstract: Based on energy equation, a one-dimensional model was used for the evolution of the temperature distribution in the GaAs target bombarded by Intense Pulsed Ion Beam (IPIB). The numerical simulation was completed according to a fitting result from the waves of the ion diode magnetically insulated and the ion current density detected by Faraday cup at the focus region of the Russian TEMP type accelerator. The parameters of the IPIB are: ion beam composing of H+ 70%, C+ 30%, average value of pulsed voltage 300kv, the maximal peak of current density of the beam 260 A/cm2, pulsed width 60ns. The numerical simulation results reveal the temperature distributing in the samples and provide quantitative informations of the first melting time at 10ns and melting layer thickness 2.4 μm after one pulse.

Abstract: An electrical conducting copper coating on the glass substrate is deposited by means of wire exploding spray coating (WESC). The coating system basically consists of a high voltage pulsed power supply and a coating chamber. A pulsed voltage is produced by the power supply upon the metal wire in the coating chamber. The whole process is under taken at atmosphere pressure and room temperature. The coating is more uniform when a higher discharging voltage is applied, which means more energy is deposited into the copper wire in the identical time, so the wire will be destructed more efficiently. A 20 kV discharging voltage is applied in this paper for the balance of coating quality and harmless to the glass substrate. The coating samples are analyzed by a series of tests. The SEM photograph shows that the copper particles penetrate deeply into the glass substrate, which results in a strong adhesion of the coating, and the thickness of the coating is about 400 to 500 μm after sprayed three times. The electrical conductivity of the copper coating is about 1.837*104 1-1·m-1 tested by a Kelvin electric bridge, and the 50 Hz withstand voltage of the glass tube before and after the spray coating is about 40 kV and 38 kV, respectively, with no obvious decrease.

Abstract: In this study, the CrN coating was first deposited on tool steels by cathodic arc evaporation technique and then this coating was subjected to oxygen glow discharge to activate the oxidation process in order to form oxide layer on the surface of the CrN coating. The varied properties of CrN coatings with or without oxidation treatment were studied in terms of hardness, adhesion, microstructure and surface morphology by using XRD, AFM, Rockwell indentation, Nano-indentation tests. The result turned out that the effect of the plasma oxidation process on the hardness of CrN coating was improved due to the oxide layer on the surface.