| 摘要 |
<p>This invention relates to thermal spraying processes and control of the injection of the powder particles into a plasma, flame, gas jet or shock front. The powder injection apparatus comprises spraying torch 12, a shroud 20 surrounding the spraying jet 13, the shroud having a powder injection port 14 and an opposing gas port 24, the gas issuing from the gas port serving to push powder particles that have passed through the spray jet back into the spray jet for further heating. Preferably, an inert gas, eg. Argon, is used as the gas so that it does not cause oxidation of the powder. Typically the heavier / larger particles (see figure 1, path 18) pass the jet and are blown back by the gas jet. A valve 22 and gas nozzle 24 may be provided to control the amount and direction of the opposing gas entering the shroud. The shroud / shield may be made from metals or ceramics.</p> |
