Parameter Development via In Situ Residual Stress Measurement and Post-deposition Analysis of Cold Spray CuNi Coatings

Developing dense, well-adhered coatings with minimal heterogeneity via cold spray deposition has been a challenge because in-flight and layer-by-layer diagnostics has not yet been adequately adapted to complement existing post-deposition analyses and parameter process mapping. This study presents an empirical and analytical approach for development and optimization of requisite spray parameters via the cold spray solid-state consolidation process using the in situ beam curvature technique to assess particle dynamics during deposition, in conjunction with post-deposition analyses. Here, CuNi (62/38) powder was deposited onto CuNi (70/30) substrates and monitored with an in situ beam curvature sensor to provide real-time feedback of the coating's evolving stress states during the deposition process and subsequent residual stress determination immediately after deposition. The resulting beam curvature compressive and tensile stress amplitudes detected layer-by-layer coating variations during deposition resulting from adjusted carrier gas flow rates, substrate surface preparations, nozzle deposition angle, robot raster speeds, powder feed rate, substrate preheat, as well as identifying nozzle clogging. The acquired stress-state data enhanced post-deposition analyses that directed and accelerated the downselection process to define and optimize cold spray parameters, as it pertained to coating adhesion, cohesion, and the corresponding microstructure.