This work assesses the potential of using an ultrasonic probe attached to the back of the substrate to monitor the cold spraying process. While this is only a preliminary study, focusing more on presenting the results than analyzing them, a few conclusions may be drawn. With acoustic sensing, not only can the final value of thickness be estimated, it is also possible to see the dynamics of how the buildup takes place in real time. As shown in the data plots, the buildup process for aluminum-alumina composites is fairly universal across the spray with slower buildup at the outer edges of the coating. More importantly, it is shown that nozzle speed, spray diameter, and thickness estimates fit well with measured values.

The corrosion behavior of Al alloys, produced by cast and powder (Low Pressure Gas Dynamic Spray or Cold Spray) technologies, was examined in 3% sodium chloride solution from the viewpoint of localized corrosion. The susceptibility to localized corrosion is known to be strongly affected by intermetallic phases present in the alloy’s microstructure. The influence of individual cathodic and anodic intermetallic phases was investigated by using a microelectrochemical setup and by electrochemical methods. The optical and scanning electron microscopy data reveal that the cast and powdered alloys experience localized corrosion due to presence of the intermetallic phases which results in the micro-corrosion effects such as exfoliation corrosion, intergranular or crevice corrosion, and most severely pitting. Cast material has lower corrosion properties because of the higher heterogeneity of the structure as compared with powder sprayed composite.