1. Field of the Invention
The present invention relates to a high-speed flame spraying gun with water-cooled combustion chamber, injection gas mixing block and expanding nozzle, in which surfaces acted upon by gas and flame exhibit a surface film with no affinity to admixed spray material or other combustion residues.
2. Description of the Related Art
Existing high-speed flame spraying guns possess a gas mixing block with water-cooled combustion chamber and an expanding nozzle connected at the outlet side. Their superiority to conventional flame spraying guns consists in the fact that the fuel gases (e.g. acetylene, propane or hydrogen) and/or the combustion gases (e.g. oxygen or air) burn in the water-cooled combustion chamber, whereby the gas expands very strongly, with the result that the hot gas stream comes out of the water-cooled expanding nozzle at supersonic speeds.
In this process, the admixed spray material (e.g. in pulverulent form), streams through the combustion chamber, whereby this material is converted into a molten or viscous state. The mixture of fuel and combustion gases also flows into the combustion chamber and is ignited upon entry of the filamentary or pulverulent admixed spray material. In this process, certain technical problems naturally arise: due to the pressure and the gas turbulence in the combustion chamber, the admixed material can not enter the opposite expanding nozzle borehole centrically--a disadvantage. In this way, molten particles of the admixed spray material are slung onto the walls of the combustion chamber or on the front side of the injection gas mixing block, where they bake on or are deposited.
These deposits also occur on the floor of the combustion chamber and in the transition area from the combustion chamber to the expanding nozzle borehole. Since these deposits are occasionally carried off by the high-speed flame and are thrown or shot onto the substratum, they can cause defects in the sprayed film to be produced. For this reason, the traditional coating procedures are not always satisfactory for certain special applications (e.g. high-tech films on airplane engines or gas turbine blades).
With the existing high-speed flame spraying gun, the injection gas mixing block, the combustion chamber and the connected expanding nozzle are normally made of copper, and those of its surfaces which are acted upon by gas and flame are given as smooth a finish as possible.