Advanced Materials Research Vols. 97-101

Abstract: Brush plated of Cu/Ni multilayer coating from a single sulfate electrolyte was prepared. The influence of applied voltage on the composition of the deposit and deposition rate was investigated to optimize the plating parameters. Wear tests were carried out in ball-on-plate geometry unlubricated. Wear scar morphology was observed using scanning electron microscopy and optical microscopy. It was found that the brush plated multilayer coating was highly dense and free from porosity. The multilayer coating showed less wear than Ni coating brush plated from the same solution. The increase in the wear resistance of the multilayer coating was attributed to lubricating effect of the transform film formed by Cu wear particles.

Abstract: The surface of U70 rails was treated by ultrasonic peening method. Keeping the electric current 1.5 A, the amplitude 24 µm and the frequency 10000 HZ during the treatment, the peening duration was 10 min, 20 min, 40 min and 60 min respectively. The wear property, wear appearance, and structural appearance of specimens have been studied by M-2000 wear tester and 6360LA scanning electron microscope. Results show that ultrasonic peening treatment can significantly improve the wear resistance of U70 rails, and the longer the peening duration, the stronger the wear resistance. The wear mass loss of the specimen with 60 min treatment is only 27 % of the one untreated. The reason is that ultrasonic peening can form plastic deformation zones. The depth of plastic deformation zones increases with the peening duration. The depth of plastic deformation zones of the specimen with 60 min treatment is nearly 100 µm. Longer peening duration means severer plastic deformation. In the plastic deformation zone, ferrite is refined to smaller grains so that the matrix is strengthened.

Abstract: Zinc coated steel, spot-welding electrode, titanium carbide, titanium diboride, coating. Abstract: TiC and TiB2/Ni were coated on the surface of cupper alloy electrodes used for spot-welding of zinc coated steel sheets by electrospark deposition to improve its lifespan. The coatings structure and phase compositions were characterized by SEM and XRD, and their life spans were examined by spot-welding test. The results indicate the major phases of the coatings are TiC and TiB2 respectively, and copper diffuses from the substrate into the top surface of the coatings during electrosparking, forming an atomic bonding between the coatings and the substrate. The electrodes are hardened by coatings. Though cracks exist, the coatings can segregate the steel sheets and the substrate and prevent zinc in the surface of steel sheets and copper in the substrate from alloying. The coatings also reduce the deformation of the electrode during spot-welding. As a result, the spot-welding lives of TiC and TiB2/Ni coated electrodes are prolonged significantly by one and two times respectively.

Abstract: Gradient Zr/ZrN/Zr layer was deposited as a diffusion barrier between the NiCrAlYSi The overlay coating and Ni-base superalloy DZ125 by arc ion plating(AIP). The microstructure and high-temperature oxidation behavior of the diffusion barrier were studied. The results show that the gradient diffusion barrier is homogeneous and compact, and has strong bond strength with the substrate. The diffusion barrier is composed of three layers, among which the inner and outer layers are rich in Zr, and the middle layer is rich in ZrN. The main phase structure of the diffusion barrier is ZrN(200). During high temperature oxidation at 1100°C, the Zr/ZrN/Zr/HY3 compound coating system presents excellent oxidation resistance.

Abstract: Carbon fibers had been modified by the method of electroless plating Ni. The surface morphology, ingredient and cross-section images of modification carbon fibers were charactered by scanning electron microscope and X-ray diffraction. A continuous dense Ni-P alloy layer could be coated on the surface of carbon fibers by such method. The nickel-plated layer expanded in a layer growth pattern. The reaction thermodynamic analysis indicated that the process was spontaneous. The controlling process of electroless plating Ni on the carbon fibers could be divided into 3 stages: at first, controlled by chemical reaction; hereafter, controlled by chemical reaction and ions diffusion; finally, controlled by ions diffusion.

Abstract: In order to improve corrosion resistance of widely used carbon steels, self-fusion Ni60 alloys coating was prepared by free-spraying and induction heating, taking 45 steel as substrate. The microstructure and corrosion resistance of the coating and the elements diffusion cross the interface between the coatings and the substrate were analyzed. The results indicate that Ni60 coating free from cracks is obtained by free spraying and induction heating. The microstructure of the Ni60 coated substrate consists of top surface, intermediate layer, dendritic crystal zone and lamellar zone from outside to inside. The corrosion resistance of Ni60 coatings is markedly superior to that of the substrate in acid and alkali solution, and surpasses stainless steel in reductive and alkali solutions

Abstract: A finite element simulation of a plasma sprayed thermal barrier coating(TBC) system was conducted. Plasma sprayed thermal barrier ceramic coating was treated as either a simple elastic model or an advanced viscoplastic model which includes rate dependence and unequal flow stresses in tension and compression. Predicted tensile stresses emerging in the ceramic plane at the elevated temperature never become large enough to cause surface cracks based on elastic analysis, so does using the viscoplastic model. At the low temperature, these two models identically show that the ceramic coat will locally cracks at the “peak” location. It is shown that although there are some numerical differences in these two models’ predictions, elastic analysis predicts accurate in failure mechanism analysis based on stresses

Abstract: The microstructure and properties of hardened layer of 45 steel disk opener with a variety of parameters of HLD1001.5 solid-state laser were studied by SEM, Rockwell hardness tester and wear tester. The results showed that under the conditions of the laser power from 400W to 600W, the hardened layer is composed of melted zone, phase transformation zone and heat affected zone, and the hardness is up to 58.5-61HRC, and the disk openers have excellent wear resistance after the laser hardening, which is best in the disk opener with the treatment of laser power 500W.

Abstract: Using a combination of high speed jet electrodeposition and plasma transferred arc (PTA) quenching, a nano-TiN/Ni composite coating on 7005 aluminium alloy can be produced. The microstructure, microhardness, friction coefficient and corrosion potential Ecorr of PTA treated specimens were investigated. The results showed that a rapidly solidified microstructure consisting of the uniformly distributed TiN phase and fine Al3Ni2 intermetallic phase was in PTA treated specimens. The results also showed that the composite coating PTA treated has an average microhardness of approximately 800 HV. The friction coefficient of PTA treated specimens (oscillated around 0.25) is considerably lower than that of TiN/Ni composite coating (oscillated around 0.35). The PTA treated specimen had the lowest corrosion current density Icorr as well as the highest corrosion potential Ecorr and showed an improved corrosion resistance compared to 7005 aluminium alloy as well as TiN/Ni composite coating.

Abstract: This paper have studied the high temperature frictional wear properties of Ni-P coatings on 20CrMo steel manufactured by electro-brush plating. A ball-on-disc configuration with no lubricants was employed and 4 mm diameter Si3N4 ball was used as static counterpart. The results showed that with the coating time increased from 0 to 24 minutes, the overall average friction coefficient and the mass worn loss of specimens were both declined in the wear test at 450 oC for 180 minutes. The wear became slighter as the coating time increased. When the coating time were 0, 6, 12 and 18 minutes, the main wear form of samples were deep microscopic plough cutting and spalling failure. As the coating time increased to 24 minutes, its main wear form were shallower microscopic plough cutting, almost no spalling failure.