In Situ Spray Bead Acquisition and Analysis for Coating Thickness Predictions

Coating thickness is considered to be one of the most important characteristics of thermal spray coatings. Therefore, it has long been the goal to be able to predict the coating thickness that ensues when coating an arbitrary part. A commonly applied approach is to determine the coating deposit based on a series of spray spot tests and use that for modeling the coating. Another option is to conduct spray bead tests, which better reflect the conditions during the coating. This work suggests a novel approach for in situ acquisition of the spray beads and their analysis. The acquisition is based on a 3D camera to scan the sample before and after depositing of a spray bead. The approach allows for their streamlined evaluation, enabling better understanding of spray bead formation and their modeling. The suggested analysis of spray beads includes uncertainty evaluation. This enables estimation of model prediction uncertainties which has been omitted in the previous works on the topic. The analysis shows that a relative expanded uncertainty of 10% (at 95% level of confidence) can be expected for the coating thickness prediction for the simplest scenario of coating a flat sample sprayed perpendicularly at a constant spray distance and spray speed.