A single-pulse experiment was conducted to study the mechanism of electrical discharge machining (EDM) ablation. An equivalent model of EDM ablation was established to explain the changes in the oxide layer of electrodes. Theoretical analysis was performed to understand the machining mechanism behind EDM ablation. Four stages and three models of EDM ablation were proposed to explain the machining mechanism of this process. Tests were performed to compare normal EDM, EDM spark-induced combustion, and EDM spark-induced explosion. The processing depth and surface morphology of the machined workpiece in the experimental results are coincident with those in the theoretical analysis results.

This paper presents an evaluation of the molten pool laser damage done to an Al₂O₃ ceramic coating. Mechanism analysis of the laser damage allowed for a 2D finite element model of laser ablation of the Al₂O₃ ceramic coating to be built. It consisted of heat transfer, laminar flow, and a solid mechanics module with the level set method. Results showed that the laser damage mechanisms through laser ablation were melting, gasification, spattering, and micro-cracking. The ablation depth and diameter increased with the increasing laser ablation time under continuous irradiation. The simulation profile was consistent with the experimental one. Additionally, the stress produced by the laser ablation was 3500–9000 MPa, which exceeded the tensile stress (350–500 MPa), and fracturing and micro-cracks occurred. Laser damage analysis was performed via COMSOL Multiphysics to predict laser damage morphology, and validate the 3D surface profiler and scanning electron microscope results.

Microwave dielectric ceramics are employed in filters as electromagnetic wave propagation media. Based on additive manufacturing (AM) techniques, microwave dielectric ceramic filters with complex and precise structures can be fabricated to satisfy filtering requirements. Digital light processing (DLP) is a promising AM technique that is capable of producing filters with high accuracy and efficiency. In this paper, monolithic filters made from Al₂O₃ and TiO₂, with a molar ratio of 9:1 (0.9 Al₂O₃-0.1 TiO₂), were fabricated by DLP. The difference in the dielectric properties between the as-sintered and post-annealed samples at different temperatures was studied. The experimental results showed that when sintered at 1550 °C for 2 h and post annealed at 1000 °C for 5 h, 0.9 Al₂O₃-0.1 TiO₂ exhibited excellent dielectric properties: ε_r = 12.4, Q × f = 111,000 GHz, τ_f = +1.2 ppm/°C. After comparing the measured results with the simulated ones in the passband from 6.5 to 9 GHz, it was concluded that the insertion loss (IL) and return loss (RL) of the filter meet the design requirements.

The surface state of metallic materials significantly affect their physical, chemical, and corrosion behavior. In the present study, superhydrophobic coating with copper deposits fabricated using a jet-electrodeposition device on the pure copper substrates for reducing the corrosion rate of the copper substrates was studied. The effect of the micro-nano structured superhydrophobic coating on the improvement of corrosion resistance was investigated. Factors including the microstructures and wetting properties of coating were comprehensively analyzed using a scanning electron microscope, a Fourier transformed infrared and a surface contact angle meter. Results showed that the superhydrophobic coatings demonstrated a micro-nanostructure on the copper substrates. After modifying the copper deposits with stearic acid, a superhydrophobic surface was consequently obtained. The static contact angle (CA) and the sliding angle of the copper-based superhydrophobic surface were 151.6° and 5.7°, respectively. The samples covered with superhydrophobic coating exhibited relatively higher corrosion potential and lower corrosion current than the bared pure copper samples, indicating a notable enhancement of corrosion resistance characterized using polarization tests by an electrochemical workstation.

Selective laser melting (SLM) is an important method in additive manufacturing. SLM has obvious advantages for the fabrication of metal parts with complex structure that cannot be processed directly and are manufactured in relatively low amounts. However, the surfaces of the SLM-formed parts contain more adhesive particles and pores than those manufactured by traditional methods, leading to the poor corrosion resistance of the parts and preventing the widespread use of SLM. To solve these problems, jet electrochemical machining and jet electrodeposition combined processing techniques were investigated for the treatment of the substrate surface in this work. Jet electrochemical machining was used to remove the surface defects of the SLM-formed parts, and the results were compared with the traditional sandblasting and sandpaper grinding surface treatment methods. Then, the nickel coating was deposited on the surface of the SLM-formed parts using jet electrodeposition to protect the surface and extend the service life of the parts. The mechanisms of the different processing techniques were analyzed, and properties such as the substrate morphology, coating morphology, corrosion resistance of the coating, and adhesion of the coating were compared. The results show that holes, adhesive particles and other defects are still present on the substrate surface after sandpaper grinding and sandblasting and affect the quality of the nickel coating. After electrochemical machining, the SLM surface defects were almost completely removed, forming a uniform microporous structure that interlocked with the nickel coating. The coating was smooth and dense and showed the best corrosion resistance and binding force. In 3.5 wt% NaCl solution, the corrosion potential reached −0.196 V, and the maximum binding force reached 35 N.

In order to lengthen the lifespan of NdFeB materials, nickel coating was manufactured by magnetic jet electrodeposition. The surface morphology, coating adhesion, and corrosion resistance of the coating were characterized and analyzed, respectively, by scanning electron microscope, scratch tester, and electrochemical workstation. The experimental results show that the surface of nickel coating which was fabricated by magnetic jet electrodeposition had no nodularity, and as a result, the surface morphology improved; furthermore, the corrosion resistance and coating adhesion of the coating improved in the effect of magnetic field intensity. When the value of the current density was 60 A/dm² and the intensity of magnetic field was 100 mT, the coating adhesion could reach the standard in 33.4 N, which was doubled compared to the coating without magnetic field. Corrosion of the coating morphology is no longer the regional corrosion. Magnetic field is beneficial to improve the quality of coating surface morphology and reduce the corrosion current density of the coating.