Possibilities for online coating thickness measurements during thermal spraying
There are several important economic factors related to thermal spraying, including the selection of the right spraying material and the desired coating thickness. For the latter it is critical to actually achieve targeted thickness as precisely as possible. Putting down too much material and exceeding the specified thickness can substantially increase costs.
Typical methods to determine the coating thickness rely on offline measurements, which either involve the interruption of the coating process, or the utilization of test samples that run in parallel to the actual part coating. Some of these methods only work for particular substrate and coating materials. Therefore concepts to measure the coating thickness during the process without the need for physical contact are of crucial importance to the cost effectiveness of thermal spraying solutions.
Fraunhofer IWS engineers evaluated the technical possibilities for simple contactless optoelectronic measurement techniques to determine the coating thickness online during the thermal spray process such as atmospheric plasma spraying (APS) and high velocity oxygen fuel spraying (HVOF). The most important task was to determine the reliability of the various methods including the data spread and possible disturbances.