| Abstract: |
Suspension sprays have been applied in high velocity oxygen fuel (HVOF) spraying process as a possible alternative of dry powders in conventional HVOF-spraying. It enables the fabrication of nano-structured coatings by the use of nanoparticles. One of the inherent problems of the HVOF process is the gas temperature is well above the melting point of the spray materials, and the materials experience oxidation while traveling in the gas flow. In order to overcome this problem, two-stage HVOF process was developed in recent years, in which the temperature of the gas flow can be controlled in a desired range. Much consideration has been given to the study of the injection of powders into two-stage HVOF process. In this paper, the injection of suspension sprays into two-stage HVOF process is investigated to explore a new spraying process. Computational fluid dynamic techniques were carried out to solve the mass, momentum, and energy conservation equations. Suspension sprays were tracked in the supersonic gas flow using a Lagrangian approach. The temperature and velocity of the flow fields, and the trajectory and heating of in-flight droplets are predicted for different operating parameters. Effects of the mixing gas flow rates, suspension injection velocity, flowrate, and concentration on this process were investigated as well.
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