Plasma spraying of submicron ceramic suspensions using a continuous ink jet printer

A novel method of manufacturing ceramic coatings by plasma spraying of submicron suspensions of zirconia was investigated. Submicron zirconia powders were dispersed in a solvent with the addition of a dispersant and used as ceramic inks for a continuous jet printer with a nozzle diameter of 50 μm. A stream of monodispersed equispaced drops produced using the printer was injected into a plasma flame to allow coatings to be fabricated. Various arc currents and gas flow rates were investigated. It was shown that splats which are similar to those produced by conventional plasma spraying, but significantly smaller, could be produced only at arc currents >750 A. Below this value the original ceramic material was clearly visible on the substrate. The most uniformly molten splats under 10 μm were produced by plasma spraying onto a hot substrate using hydrogen as a secondary gas.