How to Determine Process Fluctuations in Wire-Arc Spraying

Abstract

Wire-arc spraying is particularly used for large-area coatings due to the high cost efficiency of the process but is also characterized by strong fluctuations. Nowadays, a costly and time-consuming inspection is required after coating in order to identify and eliminate possible coating defects caused by the process instability. Therefore, a sensor unit with seven channels is established, which realizes an in situ monitoring of the process. The voltage and current sensors are analyzed in detail within this work. Additionally, a variation of the process parameters voltage and wire feed was used to compare the data of a stable and an instable process regarding the arc stability. For a deeper understanding of the process and its performance, the surface is characterized by confocal laser scanning microscopy and cross-sections are investigated by SEM as well as light microscopy. The new and so far, unique sensor unit is successfully established for the current and the voltage sensor on the wire-arc spraying process. The in situ recording identifies fluctuations of the spraying process. Anomalies of the current I were detected before the break down of the arc occurred. The parameter variation showed an influence on the coating properties. A higher voltage results in a denser coating structure.