Dynamic processes during high velocity oxyfuel spraying

Abstract

High velocity oxyfuel spraying is a new, rapidly developing technology for coating formation which is now challenging plasma spraying. Dynamic processes during HVOF spraying have considerable influence on the coating quality. The dynamic processes considered are as follows: combustion and gas dynamics, mechanical and thermal inflight behaviour of the powder particles, and droplet flattening. The corresponding literature is also reviewed. The following points are taken into account: fluid behaviour inside and outside a spraying gun; fluid-particle interactions; particle shape and morphology; internal heat conduction in powder particles; mass transfer (dissolution, diffusion, etc.) inside the composite particles; particle heating, fusion, cooling, and solidification; surface roughness, splat solidification, and mass loss of the droplet liquid phase during droplet flattening. Good agreement between theoretical and experimental results is shown to exist. The results obtained can be used for prediction of the optimum conditions of spraying.