Advanced Materials Research Vols. 154-155

Abstract: Fabrication of friction reducing and anti-wear surface with regular micro/nanostructures is a hotspot of surface engineering studies nowadays. We present a simple and easily-controlled method for fabricating stainless steel-based nanostructures surface. First, by strictly controlling the number of femtosecond laser pulses, two kinds of nanostructures are fabricated. Then, forming mechanisms of nanodots and ripple structure are analyzed. Lastly, we obtained uniform large-area nanodots and ripple structures by adjusting the repetition rate of laser focus accurately. Therefore, this technique will provide a good method to investigate the tribological properties of controllable nanotexture surface.

Abstract: With different means of soaking treatment, simple cerium conversion coating, KH560 silane conversion coating, cerium silane conversion coating and silane cerium conversion coating are formulated. SEM, EDS, Tafel and EIS measurements were adopted as the analysis approaches, and organic resin is coated on the conversion coating surface for the salt spray test, so as to check mainly how much the corrosion resistant capabilities could be improved if conversion coating is applied to the magnesium alloy. The result shows that the cerium silane conversion coating and silane cerium conversion coating have a higher self-corrosion potential, lower corrosion current density, improve the binding force between the organic coating and magnesium alloy matrix more effectively, thus enhance dramatically the corrosion resistant protection capabilities for the whole coating applied on the magnesium alloy matrix.

Abstract: Wear behaviours of micro-arc oxidation (MAO) coatings on pure aluminum in a phosphate based electrolyte were investigated. The surface morphology, cross-section morphology and elements distribution of coatings were observed by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). Wear test was proceeded with improved pin-on-disk tester under the dry sliding friction condition at load of 10 N. The results show that coatings structure are poly-porous and uniform, the components in the phosphate electrolyte do not participate in the formation of coatings, coatings are oxidized and sintered intrinsically. Wear weight loss of MAO coatings decrease by a factor of 20 in compare with the pure aluminum substrate, and abrasive wear assisted stripping from micro-cracking is predominant wear mechanism.

Abstract: WC-Ni-Cr composite cladding is fabricated on the Q235 steel by infiltration brazed in a vacuum furnace. Microstructure of interface and welding specimen's longitudinal section of alloy coating are investigated by CMM-88E metallographic microscope and FEI Quanta200 scanning electron microscope. Element diffusion and distribution along the longitudinal section are tested by the Energy Disperse Spectroscopy (EDS), produced by Oxford Corporation; Influencing factors of the coating's brazed interface are analyzed. The results show that when nickel base coating powders are used for infiltration brazed, the BNi-2 solder is appropriate and the appropriate temperature should be in 1120~1140 °C. The welding interface of vacuum brazing compact very well and the existence of element diffusing forms the metallurgy welding contact surface.

Abstract: SUS 304 used. A passive film on surface was needed to remove with anodic electrolytic degreasing in 3.0 mol/dm3 H2SO4 at 298 K. Cu film was electroplated 20 mA/cm2 in 0.5 mol/dm3 CuSO4 and 2 mol /dm3 H2SO4. Current efficiency increased when plating carried in sonication of 28 kHz after plating in stationary state. Particles were destroyed and size became smaller with shockwave pressure. Particles were pressed in pinholes, defects, etc. Surface that was obtained at 28 kHz was smooth and dense compared with other agitation states.

Abstract: Aiming at issues existed in lead-free electronic packaging, as well as the air pollution induced by volatile organic compounds (VOC) in conventional soldering fluxes, a new VOC-free no-clean flux was formulated specifically for lead-free wave soldering. Spread test and wetting balance test were carried out to evaluate the activity of the newly developed flux with Sn3.8Ag0.7Cu lead-free solder. Besides, influence of flux residues on corrosivity and reliability of printed circuit board (PCB) was investigated by measurement of surface insulation resistance (SIR). The results showed that VOC-free fluxes required a good preheat process to obtain better soldering performance. And, flux residues of new VOC-free 1 had higher corrosivity than VOC and VOC-free 2, so the flux formulations needed to be ameliorated for the future. Due to the benefits of eco-friendly and cost saving, it is promising to successful implementation of VOC-free fluxes if some process modification is done.

Abstract: Surface roughening, with certain roughness topography, is thought to be as an effective tribological method of decreasing friction coefficient of kinematic pairs. Friction and wear of AISI1045 steel surface roughened by convenient and economical way of sandblasting was investigated under lubrication conditions. Roughened and polished samples run against Φ4mm GCr15 pin lubricated by engine oil were tested in reciprocating mode with different load and speed on UMT- testing machine. It is found that there exists the optima surface roughness (Ra is about 3.92μm) roughened by sandblasting in which the least wettability contact angle between engine oil and textured steel surface is obtained, hence the lowest friction coefficient and wear rate is due to the optima hydrodynamic sliding property, although the sliding surface was not in hydrodynamic lubrication state.

Abstract: As reported in the previous report, increasing velocity by high-speed impulsive energy could improve the formability of AZ31 magnesium alloy. The improvement of ductility of AZ31 magnesium alloys can be observed, which is difficult to observe in usual cold forging techniques. This paper (Part II) is a coutinuation of the reported work in the previous paper. The forming of the AZ31 casting magnesium alloy was done. The hardness distribution of the test specimen was investigated for each experiment, and the microstructures are analyzed. The microstructural results indicate that adiabatic shear bands are formed and the microstructure is changed by the formation of huge amount of fine grained recrystallized structure. Furthermore, solid state is retained in the materials as well as the surface. [1]

Abstract: Axial turning-grinding is a processing method to cut the cylindrical workpiece along its axis, using the kinetic energy of high-speed rotation annularity tool, the abrasives in tool tip as the main cutting edge to remove materials and the abrasives in the outside surface of tool as a minor cutting edge to sharpen the processed surface. Comparing with concentric axial turning-grinding, eccentric axial turning-grinding has higher efficiency. The result indicated that cutting thickness and feed rate could be more than 5~10mm and 200mm/min respectively in a cutting, realizing high-efficiency, low-cost processing of engineering ceramics. According to axial force, chips’ shape and damage degree of surface to be processed, obtaining the proper feed rate range. Removal mechanism analyses showed that both median/radial cracks and lateral cracks occurred in the part to be removed, and the intensity of the processed part had little destroyed, only needing adjust axial force to control the length of transverse cracks.

Abstract: The door beam inside the car door is an key component to improve the security of passengers, most great automobile manufacturing companies use ultra-high strength steel plate to manufacture it，however, it is very difficult to form in room temperature，so commonly it is made by hot stamping but the cost is too high. This article gives a solution to deal with this problem by the use of FEM software in simulating and optimizing the forming process of one kind of ultra-high strength steel door beam in room temperature, and main study is in the influence of temperature on internal organization changes of the ultra-high strength sheet and springback by comparing the simulation result and real sample, and meanwhile convex roofs are added in the addendum to optimize the surface. It is helpful on how to design die face in manufacturing the related ultra-high strength steel parts.