Effects of Fuel Types and Process Parameters on the Performance of an Activated Combustion High Velocity Air-Fuel (AC-HVAF) Thermal Spray System

In the development of technology to replace chromium and cadmium, WC-12Co powder deposited by an activated combustion high-velocity air-fuel (AC-HVAF) thermal spraying technique is considered an ideal surface protection method to replace surface chromium plating. In this work, the computational fluid dynamics method is used to simulate the AC-HVAF thermal spraying process. A gas-phase model is implemented by using the renormalization group k - ε turbulence model. The combustion reaction process is calculated by combining a one-step chemical reaction model and an eddy dissipation model. A discrete phase model of spray particles is established based on the Lagrange method. The changes in gas dynamics, gas component concentrations, and particle flight features during thermal spraying are revealed. The results show that gas-solid coupling can predict particle behavior more accurately. Compared with the propane-fueled gas-phase, the hydrogen-fueled gas-phase has a lower temperature and a higher velocity. Using hydrogen fueling, the particles obtain higher temperature and velocity with increasing reactant mass flow rate and decreasing oxygen/hydrogen ratio. The carrier gas mass flow rate can control the particle temperature but does not change the particle velocity. Higher particle loading reduces particle temperature and increases particle velocity.