Prediction of Locations of Poor Splat Bonding in Multi-Traverse Cold Spray Deposition

In cold spray deposition, powder particles accelerated to several hundred meters a second impact the substrate and deform into splats that are stacked up to form dense coatings on the substrate. These deposited splats, however, are usually not fully bonded to each other, making deposited materials less ductile than wrought materials. An ultrasonic washing test, applied to Cu coatings sprayed on Al substrates, revealed poor splat bonding along spray boundaries and spray layer boundaries. Thickness measurements of coatings deposited with a single linear spray traverse yielded profiles that are approximately Gaussian curves but with reduced edges. We attribute the reduced edges of the thickness profiles to lower particle impact velocities and temperatures in the outer regions of the spray cone. A simulation model was developed that can predict locations of poor-bonded regions in coatings produced by multi-traverse cold-spray deposition from experimentally determined thickness profiles of single-traverse coatings.