Construction and application of a small-sized spray apparatus utilizing electrothermal explosion of spray powders to a study on the production of refractory spray coatings

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A small-sized apparatus utilizing the electrothermal explosion of electrically conductive powders was constructed for the production of refractory spray coatings. It sprayd carbide, boride and nitride ceramic powders with melting points higher than 2800K.Thus, some novel results were found below ;1. Spray of tungsten carbide and tantalum carbide : In order to produce dense and adhesive coatings of these carbides, the flow density of the ceramic jets was increased. Then the mixing of sprayd ceramics and substrate metals ranged 30 to 50mum. In addition, the top coat of monolayr ceramics was obtained over the mixing layr. Such a graded coating was expected to be highly adhesive on metal substrates.2. Spray of titanium boride and nitride : The increase of energies supplied to these ceramic powders resulted in the dense coatings with mixing layr of the ceramics and metal substrates. The graded coatings with top monolayr ceramics were obtained by the repetition of the spray. However, nonstoichiometry of nitrogen happened in the nitride.3. Composite coating by reactive spray : The electrothermal explosion of a mixed powder of titanium and hexagonal boron nitride resulted in the composite coating of titanium boride and nitride ceramics. Such ceramics mixed with the surface of metal substrates.