| Abstract: |
In thermal spraying, the material feedstock (commonly a powder, wire or suspension ) is injected in an enthalpic source (thermal plasma or flame obtained by ionization-excitation of inert gases or combustion, resp.). The particles are melted (or partially melted), accelerated by a gas flow, and crushed on the target substrate where rapid solidification and deposit built-up occur.
For separated heating of the deposited material and surface the method of laser thermal spraying using conical laser beams has been elaborated. Initial round laser beam is divided into 2-3 circular beams with regulated distribution of the laser power throughout the circular beams. Circular beams are transformed to conical beams , which are focused separately on the surface and on the deposited material ( powder stream, wire, suspension stream ) for heating . A focuses of conical beams are arranged along the optical axis by which the deposited material is fed. The calculations and modelling demonstrate that the new method of the independent energy input to powder stream and surface using conical laser beams is more efficient because heating of small particles at stationary mode of operation and a total uniform absorption of laser beam energy is possible in the dense powder stream. The optimal regimes of laser thermal spraying can be achieved using multipass optical scheme and conical beams with different wavelengths. New method also allows significantly raise parameters of the cold spray coatings and efficiency of the cold spraying. The efficiency of the laser thermal spraying can be 10 - 102 time higher than other thermal spray technologies. New method is absolutely environmentally friendly, unlike other methods of thermal spraying.
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