Experimental Study On Coating Produced By Wire Electrothermal Explosion And Material Synthesis In The Constrained Capillary Tube

In recent years, electrical explosion has been applied in the areas of material synthesising and spraying, especially for its advantages in spraying. Wire explosion has small heat affection on the substrate in the spraying process. The coating , being compact, uniform, and well-bonded with substrate, is fit for spraying high-melting metal meteria. Wire electrical explosion spray is free explosion, the product of which is sprayed on the substrate when it expands with high velocity from the explosion central area to all around. It characterized by its well-directional spraying and high utilization ratio of material, is also an oriented spraying method developed on the basis of free wire explosion. If the wire electical explosion was constrained , namely, the electric conductor material is put in the capillary tube for electrical- thermal explosion, the product can form a better oriented spray under the constraint of the capillary tube. In order to study the approach of electrical- thermal explosion and material synthesising under the constraint of the capillary tube, we devise a constrained tube by insulated polyethylene with one end open and the other closed, with inside diameter of 7 mm and length of 80 mm. There were electrodes at both ends of the inwall of this tube and the conductor was put between the two electrodes. In the process of the experiment, the outer high voltage pulse set a high-voltage electric field between these two electrodes. Pulsed large current affect the conductor through both electrodes, which makes the conductor explode. Due to constrained by the tube, coating forms on the the subtrate by electrical explosion spraying constantly at the open end and crash in extreme high velocity.We chose Mo wire with the diameter of 0.2 mm as the conductor and carried out a series of tests on the surface of the steel under certain experimental parameters. We also analyz the form mechanism of the coating. The results showed after spraying on the substrate, the product of Mo wire in the constrained tube could form a spraying spot formed with a central coating zone and outer bonding layer by a single electrical explosion spray. When the spraying distance was certain, the central coating, being compact and uniform, well-bonded with substrate, formed metallurgical bonding, and the diffusion occured in the interface between them. When the spraying distance became farther, the outer adhesive layer vanished. Large coating could be formed by overlapping the single spraying spot reasonably, and thick coating could be obtained by spraying several times.At present, the main method for synthesisizing nanometre diamond is normal slice catalyst synthesis, synthesizing with catalyst powder, explosive synthesis, electrical-thermal chmeical, etc. In order to study the property and phase change of the product which formed by high energy density on the carbon material, we used a constrained tube in an electrical explosion setup. When the electrical explosion of graphite powder was carried out with the energy density of 7.77 J/mg for experiments, electrical explosion product is analyzed by Raman spectrum. In the laboratory we measured obvious characteristic peaks in the spectrum at 1332 cm-1 and 1325 cm-1. This preliminarily implys that diamond or diamond like carbon is produced by electric explosion of graphite powder in large energy densities. However, this process still needs a lot of experimental demonstration. The productivity and quality of diamond produced by electric explosion of graphite powder is still under further research.