Acoustic Emission Analysis of Twin Wire Arc Spraying (TWAS) Using Cored Wires with Different Powder Size

One of the greatest hindrances of the wide distribution of thermal spraying techniques is the missing online control over the spraying process. An optimization of thermally sprayed coatings is largely determined by an empirical modification of these spraying parameters and the subsequent correlation of parameters to the obtained coatings. Some intrinsic parameters, such as fluctuations in twin wire arc spraying and wear in the atomization nozzle, are not adjustable. Even though they have an enormous impact on the obtained coating quality, they are scientifically often neglected for reasons of simplification. In this work, acoustic emission analysis is utilized to study the effect of uncontrollable parameters on the acoustic signals. In order to enable an easy determination of the changes in the acoustic signals, the acoustic sensors were mounted on the spraying nozzle as well as on the substrate. At increased current, a lower acoustic emission is recorded. A correlation between uncontrollable parameters, the acoustic signals and the obtained coating quality was observed. This research contributes to the online control over the spraying process.