Control of thermal spray processes by means of process maps and process windows

A general method to map and control thermal spray processes, ensuring predefined levels of selected final coating properties, is presented. The method relies on monitoring and individually controlling particle velocity and particle temperature through selected spray gun parameters. Mapping of the process results in process maps describing the individual effect of particle velocity and particle temperature on each selected coating property of concern; in this case, different features of the microstructure and deposition efficiency. From the information provided by the process maps, a process window is constructed. This process window provides the limits within which particle velocity and particle temperature are allowed to vary to fulfill a predefined coating specification. To verify the method, two predefined thermal barrier top coatings one porous and one dense-were produced by air plasma spray with satisfactory results.