How are thermally sprayed coatings created/built up?
A molten particle or a particle able to deform plastically is transported at high speeds within a heat source towards a surface upon which deposition occurs. The droplet or particle undergoes spreading and may create a chemical bond with the underlying surface. With materials that are not able to produce a chemical bond, the substrate is roughened to create a mechanical bond. Each droplet or particle impacts a roughened surface and mechanically interlocks with the asperities on the underlying surface.