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In this study, a (Ti + graphite)-Ni composite powder serving as a coating material was deposited on H13 steel to fabricate an in-situ TiC-reinforced Ni-based composite coating by a new type of ESD process, which was named ultrasonic-assisted electrospark powder deposition (UEPD). The composite coating has an average thickness of approximately 45.5 μm and metallurgically bonds with the substrate. The ultrasonic vibration exerted on the UEPD electrode can effectively improve the forming quality of the composite coating, which produces better compactness and thickness uniformity as well as few defects. The microstructure mainly consisted of submicron dendrites due to the rapid solidification of the molten pool. TiC particles as reinforcements were successfully synthesized in the coating via an in-situ reaction due to their low Gibbs free energy and high melting point. The formation of refined grains and in-situ reinforcements prompts the average hardness of the coating to reach 1400.5 HV0.05, which is approximately 2.5 times that of the substrate. The tribological properties of the composite coating are greatly improved in comparison with those of the substrate. The wear rate and friction coefficient of the composite coating decrease by two orders of magnitude and 46.2%, respectively. [ABSTRACT FROM AUTHOR]

Almost differences sets have important applications in cryptography and coding theory. In this paper new families of almost difference sets are constructed. Some necessary conditions for the existence of (v, k, [lambda],l)-almost difference sets in [Z.sub.v] are derived.

The applicability of micro-electrical discharge machining (micro-EDM) using laminated 3D microelectrodes to eliminate defects such as numerous micro-stripes that are prone to appear on the sidewalls of microstructures manufactured via micro-electrochemical machining (micro-ECM) was examined. The study proposes the fabrication of 3D microstructures with laminated 3D microelectrodes through micro-EDM with deionized water containing B4C powder having a particle size of 1 μm. First, the effect of different machining voltages, B4C concentrations, and microelectrode back-off distances on the unilateral gap was investigated. The results indicated that a machining voltage of 100 V, a B4C concentration of 3 g/L, and a microelectrode back-off distance of 200 μm resulted in a 69 μm unilateral gap of the 3D microstructures. Given the effect of micro-EDM and that B4C is a semiconductor, the plasma discharge channels were enlarged, and the material removal was uniform. This significantly improved the machining efficiency. Furthermore, the polishing of B4C on electrode surfaces and workpiece surfaces smoothly removed the processing attachments with dielectric and ensured efficient and stable machining. Based on the optimized process parameters and after 1.5 h, 3D microstructures with a depth of 800 μm with a square-shaped blind hole and with semicircular and rectangular islands were obtained, and the corresponding roughness (Ra) of the bottom surface was 0.389, 0.388, and 0.392 μm. However, the corresponding microelectrodes wear was low and approximately corresponded to 20, 15, and 15 μm. [ABSTRACT FROM AUTHOR]