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(11) | EP 0 375 931 A3 |
(12) | EUROPEAN PATENT APPLICATION |
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(54) | High velocity powder thermal spray method for spraying non-meltable materials |
(57) A method for producing a dense and tenacious coating with a thermal spray gun including
a nozzle member (54) and a gas cap (14). The gas cap (14) extends from the nozzle
(54) and has an inwardly facing cylindrical wall defining a combustion chamber (82)
with an open end and an opposite end bounded by the nozzle. An annular flow of a combustible
mixture is injected at a pressure of at least two bar above atmospheric pressure from
the nozzle coaxially into the combustion chamber. An annular outer flow of pressurized
air is injected from the nozzle adjacent to the cylindrical wall. Powder particles
having a heat-stable, non-fusible component and a heat-softenable component, and entrained
in a carrier gas, are fed axially from the nozzle into the combustion chamber. An
annular inner flow of pressurized air is injected from the nozzle into the combustion
chamber coaxially between the combustible mixture and the powder-carrier gas. Upon
combusting the annular mixture a supersonic spray stream containing the powder is
propelled through the open end to produce a coating. |