Abstract

Thermal Spray Coatings were prepared by the electrothermal explosions of ceramic powders caused by high-voltage electrical breakdown and large-current Joule heating. The powders of tantalum carbide, tungsten carbide and titanium carbide were sprayed without any additives. Even these hard-sintered materials could be densely deposited to form their coatings on metal substrates. The deposits ranged several tens tm in thickness. The Vickers microhardness of the coatings was much closer to those of the ceramics. This new spray technique employed a powder container which was especially designed in order to heat effectively the powder up to its melting point. The increase of tensile strength of the powder container enhanced the heating of the ceramic particles and jetting of them from the container. Thus the mixing of the sprayed ceramics with the substrate surfaces was obtained in the range of a few tens ìm. However, the decarburization of the TaC and TiC powders were caused under the spraying, followed by the change of lattice constants. The deposition of WC coating resulted in phase change due to the decarburization.

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