Papers by Keyword: High Velocity Arc Spraying

Abstract: Electrochemical impedance spectroscopy (EIS) is a technology of nondestructive electrochemical testing. In this paper, EIS is applied to study the corrosion processes of Al-Mg coatings. In the initial 24 h of immersion in 3.5% NaCl solution, passive films of Al-Mg coatings dissolve quickly. As time passed, corrosion products increase on surface gradually, which can inhibit corrosion. After 480h of immersion, corrosion products fully cover on Al-Mg coatings’ surface. The EIS of different corrosion processes are fitted by three equivalent circuits corresponding to the three corrosion processes. In the test of open circuit potentials (OCP), OCP is instable in the initial 24 h of immersion. As immersion time goes by, OCP tends to stabilization at about -0.90 V. Measurements of scanning electron microscope (SEM) confirm the conclusions of electrochemical measurements.

Abstract: The Tribological properties of FeCrNi/CBN composite coating with spraying high velocity arc is studied. Images and components and cross-section microstructure of coatings are analyzed by the means of SEM, and EDS etc. This research indicates that FeCrNi/CBN composite coatings have typical layered structure characteristic and high bond strength and hardness. Friction coefficient of coatings at room and high temperatures have “Run-up” period. With the increase of temperature, friction coefficient of coatings becomes low and wearing capacity of coatings becomes high. The adding of CBN powder highly improved the wearing capacity of coatings.

Abstract: A kind of self-shielded carbonitride alloying flux-cored wire was developed. Wear resistant coatings was prepared on the surface of the Q235 low-carbon steel by HAVS using the wire. Detection and analysis on the microstructure and properties of the coatings were done by the equipments such as scanning electron microscope, microhardness tester and wear tester. The forming, the wear resistance and its mechanism of the coating were studied. The results show that the coating has good forming property, uniformity of microstructure and compact structure, but the coating also has large oxidate and porosity, this may due to gasforming and slagforming constituents in the wire; the coatings has high hardness, the average microhardness value reachs 510 HV0.1, and the highest value up to about 560 HV0.1; the coatings has good abrasive wear performance and bonding strength.

Abstract: Two kinds of high-entropy alloy coatings of FeCrNiCoCu and FeCrNiCoCuB were deposited on AZ91 magnesium alloy substrate using high velocity arc spraying technology. Microstructure and general mechanical properties of the coatings were investigated with Scanning Electronic Microscope (SEM), X-Ray Diffraction instrument (XRD), microhardness tester and strength bond tester. The results show that the two kinds of coatings exhibit compact layered microstructure and the phase lattice type are both FCC, the microhardness of the FeCrNiCoCu and FeCrNiCoCuB coatings are 414HV0.1 and 342HV0.1 respectively, the bond strength are 36.9 MPa and 33.6 MPa respectively.

Abstract: A new automatic high velocity arc spraying system was developed. The system was consisted of five units, i.e. central control unit, operating machine, positioner, touching screen and high velocity arc spraying equipment. The central control unit is controlled by a program, controlling other four units. Spraying parameters could be input and modified on the touching screen during spraying. The moving of spraying gun was carried out by motion arm of the operating machine. The rotational velocity and angle of components to be sprayed was controlled by positioner. The spraying process for a cylinder body of automobile engine with the system was introduced in detail. The auto and manual arc spraying have been used to fabricate coating. The microstructure of the coatings prepared by the two spraying processing was analyzed. The result shows that the auto sprayed coating has a more uniform and compact structure than that of the manual sprayed coating.

Abstract: Cored wires and high velocity arc spraying (HVAS) technologies have been applied to produce Zn-Al-Mg-RE coating on A3 steels. The durability of coating in terms of corrosion resistance is the focus of this paper. The detailed degradation mechanism has been investigated using electrochemical-monitoring techniques supported by precise pre-test and post-test microscopical examination using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). Zn-Al-Mg-RE coating shows a typical aspect of layered heterogeneous structure, the existing of ZnAl2O4 and MgAl2O4 implies the good anti-corrosion feature. The polarization curves showed that Zn-Al-Mg-RE coating exhibits passive behavior at 0.5h and 16h immersion, but at 600h, it begins to dissolute. In contrast, the anti-corrosion performance isn’t cut down. The corrosion potential moves to the noble direction step by step, along with the current density drops gradually. After corrosion, it has been observed that the coating surface is jointed by flaky lamellar products and dense without obvious defects and pores. It is postulated that with the addition of RE, the porosity of the coating is reduced, meanwhile, the stability of the products layer can reinforce the self-sealing effect of the coating distinctively.