Understanding the cold spray deposition efficiencies of 316L/Fe mixed powders by performing splat tests onto as-polished coatings

Some of the current trends in cold spray include the production of metal-metal composite coatings; however, the deposition mechanisms of mixed powders are often vaguely understood. In this study, single component 316L stainless steel and Fe coatings, as well as composite 316L/Fe coatings, were deposited through cold spray and the deposition efficiencies (DE) were measured. The composite coatings featuring various feedstock fractions were produced using a dual powder feeder setup. Splat tests were then performed on the as-polished coatings to investigate the deposition behavior of each component powder on the previously deposited layers. Bond ratio (BR) was determined from the splat tests to correlate with DE. Results show that the 316L powder has a better DE than Fe; whereas the DE of 316L/Fe mixed powder increases with increasing the mixture feedstock Fe fraction. The BR was found to correlate well with the DE of both single component and mixed powders. For the individual deposition behavior of the component powder, the BR of 316L monotonically decreases on the composite coating with an increasing Fe fraction; while the BR of Fe plateaus at a relatively high value regardless of the composite coating composition, which results in the overall increase of mixture DE.