Search Results (3)

Due to many factors, the electrical explosion spraying process is not stable, which directly causes unstable coating quality and structure. Electron beam treatment may be used to improve the surface and modified structure of coatings sprayed by electrical explosions. In this study, a new TiB₂–Ag metal matrix composite coating was deposited by electrical explosion spraying and modified by electron beam treatment. The prepared coatings were characterized by surface macro- and microanalysis, XDR, cross-section SEM, and TEM. The composition of the spray-coating phase differs from sample to sample. The electron beam treatment normalized the phase composition. Ag TiB₂ B₂O became the main phase in the modified coating. Increasing the pulse energy density and duration leads to a reduction in the low-melting Ag phase and the formation of copper contact phases due to heating and melting of the copper substrate by excess electron beam energy. The coating structure consists of a silver matrix and TiB₂ inclusions. The electron beam treatment did not affect the structure; however, the microstructure of the coating transformed into a cellular crystallization structure. The silver matrix nanostructure was transformed into a nanocrystalline structure with an average crystal size ranging from tens to hundreds of nanometers. Full article

Fe-Ni-based nanocrystalline coatings with unique magnetic properties are widely used as soft magnetic materials and usually act as the core component in electronic devices. Nanocrystallized particles and thin films have become a popular contemporary research direction. Electrical explosion, characterized by an ultrafast atomization and quenching rate (dT/dt ~ 10⁹–10¹¹ K/s) for the material, is a unique approach for the rapid “single-step” synthesis of nanomaterials and coatings. In this study, experiments were carried out with intertwined wire under a directional spraying device in atmospheric Ar ambience. Two load systems of Fe-Ni and Fe-Ni-Co were considered in this work. Electrical parameters and high-speed camera images were obtained to reveal the physical mechanism and dynamic process of explosive spraying. The morphologic and crystallographic results were characterized by SEM and XRD. The magnetic properties were measured via VSM equipment, and the parameters of saturation magnetization M_s, residual magnetization M_r, and coercivity H_c were emphasized in the hysteresis loop pattern. The experimental results indicate that a dense coating was prepared with extremely low porosity, and the morphology of the coating surface shows different regions characterized by solidified chunks and loose particles. XRD patterns showed that crystalline structures were discrepant under two load systems with different Ni weight proportions. Magnetic measurements gave a thin and narrow hysteresis loop, which represents loops with good soft magnetic properties. Quantitatively, coercivity H_c decreased from 59.3 to 52.6 and from 121.0 to 49.9 for the coatings not containing and containing Co under parallel and perpendicular fields, respectively. Full article

In order to reduce the influence of polar zone effect in cross-coupling arc by changing inter-wire arc (IWA) configuration, the influence of polarity arrangement of the IWA on droplet transfer was studied. The change of voltage-current waveform and the process of droplet transfer were recorded and analyzed by a high-speed camera and electric signal synchronous acquisition system. The results show that when the IWA polarity is arranged as anode on the bottom and cathode on top, the anode spot force always promotes the droplet transfer and reduces the critical current value of spray transfer. However, with the increase in the input voltage of the IWA, the resistance of the cathode spot force becomes obvious, which hinders the droplet transfer. While the IWA polarity is arranged as anode on top and cathode on the bottom, increasing the input voltage of the IWA obviously reduces the plasma arc voltage. The critical current of spray transfer increases in anode droplet, while the cathode droplet is mainly globular transfer, and there is no spatter explosion process. Through a comprehensive comparison of the droplet transfer process of anode and cathode under the different IWA polarity arrangement, the process of anode and cathode in the IWA polarity arrangement of the anode on top and the cathode on the bottom is more stable than that in the IWA polarity arrangement of the anode on the bottom and the cathode on top, mainly because the cathode spot force under high current do not hinder the cathode droplet. Full article