High velocity oxy air fuel thermal spray apparatus

The apparatus comprises a labyrinth mixing device designed to mix a first oxidizer gas and a fuel under pressure, and to inject the mixture produced in a combustion chamber, a torch's main body (1) housing the labyrinth mixing device (2) and connectors (7) for fuel and oxidizer gases, a torch's front part (3) defining, with the labyrinth mixing device (2), the internal geometry of the combustion chamber (4) comprising several second oxidizer gas injectors (32,33) for injecting separately a second oxidizer gas upstream in the combustion chamber to promote the combustion process and connecting down-stream to a gas expanding nozzle (50) designed to receive products of combustion of said mixture and form a high-velocity gaseous jet, an ignition device (30) to start combustion of said mixture, a material delivery device (6) designed to inject an spray material axially into said high-velocity gaseous jet. The labyrinth mixing device (2) comprises one or more flanges (23,24) which define one or more mixing volumes (21,22) and holes (25,26,27), concentrically placed both on the flanges (23,24) and passing through the mixing device (2) and opening at the downstream end of the mixing device (2) for connecting a feeding section (20) of the labyrinth mixing device (2) with the combustion chamber (4). The labyrinth mixing device (2) comprises a crossing axial bore (28) to inject the spray material into the combustion chamber (4).