Ultrasonic Consolidation Post-Treatment of CuNi:Cr₃C₂-NiCr Composite Cold Spray Coatings: A Mechanical and Microstructure Assessment

The traditional role of cold spray coatings lays in the dimensional restoration of assorted components and machine parts, but these repairs often result in coating mechanical properties that fall short when compared to the parent material. A potential solution to improve mechanical properties, while maintaining the benefits of a complete solid-state process where temperatures remain below the metallic melting point, is by incorporating ultrasonic consolidation as a post-treatment process in conjunction with the cold spray coating. In the work presented here, ultrasonic consolidation was applied upon two metal matrix composite cold spray coatings consisting of mechanically blended feedstock of Cu-38 wt.%Ni and Cr₃C₂-30 wt.%NiCr at 50:50 and 25:75 wt.%, respectively. Metallography and mechanical testing were performed to analyze coating response to the ultrasonic consolidation process, which included mean free path relationship of the reinforcing particles (Cr₃C₂-NiCr). The results demonstrated an increase in tensile and adhesion properties attributed to the ultrasonic consolidation step, as well as the influence of the increased Cr₃C₂-NiCr content. Ultrasonic consolidation applied as a post-treatment upon cold spray coatings was found to provide a unique approach to complete solid-state processing where coating mechanical properties can be improved and/or modified with carbide containing particle content within the metal matrix.