Advanced Materials Research Vols. 154-155

Abstract: Pseuado Zn-Al alloy coatings were made by using of dissimilar metal wire arc spraying technology on the surface of the steel Q235 and the H2S corrosion experiment was carried out on the coatings. The corrosion rate was calculated with weight-loss method. The configurations of Zn-Al coatings before and later suffered corrosion were observed with scanning electron microscope, and the coating surfaces were analyzed with energy spectrum. The corrosion potential of the coatings was tested by using the electrochemistry testing system. The corrosion results showed that Zn-Al coatings can protect the covered steel surface and the steel substrate exposing in the corrosion environment. Being processed with pore sealer, the coatings have shown more excellent corrosion resistance.

Abstract: A series of experiment were performed to test the cleaning ability of different alkane emulsion for Si3N4 ceramic grinding. The experiment results showed that the adsorption film surface of nonpolar alkane have strong attraction to Si3N4 abrasive dust, which will make abrasive dust to gather at the grinding area and finally led to jam. To add alkane grinding fluid with polar organic substances is beneficial to decrease jam. The best additive for anti block is which integrate hydrophobic group and hydrophilic group, both are indispensable.

Abstract: The experimental research on CBN grinding wheel mechanical dressing assisted by ultrasonic vibration was carried out. Experimental results showed that ultrasonic vibration dressing is capable to improve surface topography and roundness of CBN wheel as other untraditional dressing methods. Compared with traditionally mechanical dressing, the counts of static effective grains of CBN grinding wheel dressed assisted by ultrasonic vibration increased clearly and it had clear relationship with the acoustic parameters and the dressing lead. The grains had a large protrusion height and kept good integrity after ultrasonic dressing. The technology of vibration dressing is able to prepare precisely the CBN grinding wheel.

Abstract: A kind of triple micro-displacement magnification mechanism was designed according to the magnification principle of lever. Introduced the magnifying principle of the mechanism, analyzed the magnify ability and the relation between magnification times and exterior load, deduced the calculational equation of precise magnification times pass the analyes of stress, and used the Abqus to carry on finite element simulation. The result of simulation indicates that there existed certain difference between the value of theoretical computation and finite element simulation, the value of finite element simulation is less than theoretical computation, and the D-value enlarges along with the enlarge of exterior load. There are linear relationgship between magnification times and exterior load.

Abstract: In order to investigate the effect of load and sliding speed on the tribological performance of epoxy bonded self-lubricating coatings on the metallic surface, a series of wear tests of the coatings containing MoS2 and graphite under dry friction conditions were carried out with different loads and speeds. The results showed that the appropriate load and speed are favorable to the formation of the solid lubricating film on the coating surface and the transfer film on the counterface, which make the coatings have better self-lubricating performance and the friction counterparts run steadily. The load carrying capacity of the surface adhesive self-lubricating coatings decreases as the sliding speed increases.

Abstract: Diamond-coated drawing dies are considered as ideal drawing dies for their unique characteristics, such as high hardness, wear resistance and low friction. In order to optimize the parameters of diamond coated drawing dies, this study conducts a finite element method (FEM) simulation to calculate the von Mises stresses distribution on the interior-hole surfaces of diamond coated drawing die during the copper wire drawing process, and then refines the diamond coated drawing dies based on the simulation results. Furthermore, the drawing performance of the optimized diamond coated drawing die is examined in a real production of drawing copper wires, and the results show that its working lifetime increase by a factor of 12 comparing with the conventional tungsten carbide drawing die.

Abstract: The numerical thermal mechanical simulation of radial forging process of C45 steel stepped shaft with GFM forging machine was carried out by three dimensional finite element method DEFORM 3D. According to effective plastic strain, mean stress and mean plastic strain distribution of the radial forging process, the forging penetration efficiency (FPE) was studied throughout. The results show that: effective plastic strain in the center of the forging is never be zero; The mean stress in the center of the workpiece is proposed to describe hydrostatic pressure in this paper. There is compressive strain layer beneath the surface of the workpiece, while there is tensile strain layer in the center of the forging. These studied results could be a valuable reference for designing the similar forging operations.

Abstract: This paper mainly introduces present research on the black passivation process of galvanized coating and its application. Additinally, a feasibility study on black chromium-free passivation technology for Zinc plating coating has also been discussed.

Abstract: Pulse Current Heating (PCH) process is a new method characteristic with shorter time and lower temperature to the fabrication of materials. In the present paper, the PCH was used to join Cu/Fe. The microstructures of the joined samples were observed by optical microscope, the diffusions of elements near the interfaces were made qualitative and quantitative analyses by Electron Probe Mechanism. Diffusion coefficients of Cu and Fe at PCH and Radiation Heating (RH) joining methods were compared. The results showed that, the transition layer widths were from 5 to 8 μm when the Cu/Fe joined at 750 to 850°C under 5 MPa pressure with holding times 5 or 10 or 15min. Width of the transition layer increase with the increasing of joining temperature and the extension of holding time. The initial interface will move from the Cu side to the Fe one due to the Kirkendall effect. The diffusion coefficients both of Cu and Fe to PCH joining were larger by three orders of magnitude than those of RH joining. The differences between the two methods were analyzed from dynamics and thermodynamics.

Abstract: Self-lubricating Ni+h-BN coatings were prepared by CO2 laser cladding with powder mixtures of Ni60 and h-BN. The chemical compositions and microstructures of the coatings were analyzed using SEM and XRD. The microhardness of the coatings was measured on a microhardness tester. It was found that the morphology of CrB was changed from irregular block-like shape (in Ni60+5%h-BN coating) →short–plate structure (in Ni60+10%h-BN coating)→dendritic-plate structure(in Ni60+15%h-BN coating) with increasing the content of h-BN. The microhardness of the 5,10 and 15% h-BN coatings ranged from 650～800HV0.2, 800～1010HV0.2 and 1000～1200HV0.2, which was higher than that of Ni60 coating and substrate.