High velocity powder thermal spray method for spraying non-meltable materials

摘要

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.