Cold Spray Process Monitoring and Layer Buildup Planning with Optical Profilometry

In cold spray additive manufacturing, there is a strong interest in using beads, also referred to as single-track profiles, to predict deposit thickness and establish build-up strategies for a given part. Such strategy, however, must consider effects of process inputs and other unsought parameter variations that, if left unmonitored, would affect the predictions. The present work reports on the use of optical profilometry as a method to monitor the effects of stagnant gas pressures and nozzle wear on the geometry of cold sprayed nickel bead profiles. The results show that profile features such as height and width can be well predicted by regression models that depend on process data like particle in-flight velocities, powder feed rates and spray pressures. Correlations between bead geometry, process inputs, and microstructural features observed by metallographic analysis are presented. It is shown that knowledge of bead height and feed rates can be used to predict the coating deposition efficiency with a 5% error margin. The use of profilometry to establish build-up strategies and predict geometrical coating features is demonstrated.