Parameter Development via In Situ Residual Stress Measurement and Post-deposition Analysis of Cold Spray CuNi Coatings
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PEER REVIEWED
Parameter Development via In Situ Residual Stress Measurement and Post-deposition Analysis of Cold Spray CuNi Coatings Robert F. Brown1 • Gregory M. Smith2 • John Potter1 • Timothy J. Eden1
Submitted: 10 July 2020 / Accepted: 6 October 2020 ASM International 2020
Abstract 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.
& Robert F. Brown [email protected] 1
The Pennsylvania State University, 3075 Research Drive, State College, PA 16801, USA
2
Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375, USA
Keywords chrome carbides cold spray copper nickel residual stress
Introduction Over many years of development, thermal spray (TS) parameter optimization has been enhanced through coupled in-flight particle diagnostics and other process monitoring techniques to measure particle-state parameters, such as temperature and velocity, and combined with destructive sample analyses to create process maps, process–structure– property correlations and ultimately produce the requisite coating (Ref 1-4). However, implementing traditional TS in-flight particle diagnostic equipment with cold spray (CS) application is challenging due to short nozzle standoff distances and need for supplemental particle illumination. To overcome some of these challenges, numerical analyses and modeling have been used as the primary forecasting tools for CS parameter development coupled with postdeposition destructive testing (Ref 5-8). Other direct process diagnostic techniques include in situ curvature measurements, which have been employed with various thermal spray processes to measure real-time coating stress evo
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