Correlation between particle size and porosity of Fe-based amorphous coating

The relationship between the particle size and porosity of an Fe-based amorphous coating that is fabricated using a high-velocity oxygen fuel (HVOF) process was revealed by both numerical and experimental methods. A computational fluid dynamics model was implemented in order to understand the gas-flow field and the behaviour of in-flight particles with different particle sizes during the HVOF spray process. By analysing both particle velocity and temperature, the optimal particle size range (20-30 mu m) to achieve low-porosity coatings was predicted. These calculations were experimentally verified by the production of a low porosity (0.95%), Fe-based amorphous coating that was fabricated by HVOF using the predicted optimal particle size.