Numerical Simulation And Research On Gas-solid Two-phase Flow Behavior In High Velocity Oxygen Fuel Thermal Spray

High velocity oxygen fuel (HVOF) thermal spray technology is able to form high strength, low porosity coating, mainly because the formation of high-velocity and high-temperature combustion products are recompressed and expanded through the Laval nozzle to achieve supersonic expansion. High-velocity and temperature particles are translated semi-molten or molten state, which are impacted to the substrate to form a superior coating performance. Therefore, the gas-solid two-phase flow research in the HVOF thermal spray process is particularly important.Papers of simulation analysis at home and abroad mainly in ANSYS CFX or FLUENT for HVOF thermal spray process is used material transform reaction model. In the article, the fundamental theory about internal two-phase flow in HVOF thermal spray is introduced. And the mathematic model of gas-solid flow is founded, analysis of the reaction chamber is solved with the PrePDF pre-treatment process, the entire process of HVOF thermal spray is simulated with FLUENT6.3 software, the analysis of simulation results are observed in the post-processing software.In this paper, beginning with the basic theory of two-phase flow and transport equation, the gas flow field of the mathematical model is established in the HVOF thermal spary. In FLUENT software, turbulent flows and reaction process are solved with k-? turbulence model and the non-premixed combustion process model. The numerical study includes the progress of supersonic combustion flame spray reaction, burning material content ratio, the structure of spray parameters on the flow field of gas analysis, the gas analysis of the shock wave and mach cone mechanism; based on gas flow filed, the dynamics of flight spray particles behavior is tracked with the discrete particles with random orbit model to research particle size and particle injection velocity on the dynamic behavior of particles. The results associated with foreign literature are compared , the selection of the spraying process parameters and FLUENT simulation is in widely used in HVOF spray progress to provide useful information, and finally study the melted state of particles and flat particle collision process,it shows that the best flat behavior in the WC-17Co coating for Cr12 steel substrate is at the spraying distance of 342mm.