Characterizing Suspension Plasma Spray Coating Formation Dynamics through Curvature Measurements
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Suspension plasma spraying (SPS) enables the production of variety of microstructures with unique mechanical and thermal properties. In SPS, a liquid carrier (ethanol/water) is used to transport the sub-micrometric feedstock into the plasma jet. Considering complex deposition dynamics of SPS technique, there is a need to better understand the relationships among spray conditions, ensuing particle behavior, deposition stress evolution and resultant properties. In this study, submicron yttria-stabilized zirconia particles suspended in ethanol were sprayed using a cascaded arc plasma torch. The stresses generated during the deposition of the layers (termed evolving stress) were monitored via the change in curvature of the substrate measured using an in situ measurement apparatus. Depending on the deposition conditions, coating microstructures ranged from feathery porous to dense/cracked deposits. The evolving stresses and modulus were correlated with the observed microstructures and visualized via process maps. Post-deposition bi-layer curvature measurement via low temperature thermal cycling was carried out to quantify the thermo-elastic response of different coatings. Lastly, preliminary data on furnace cycle durability of different coating microstructures were evaluated. This integrated study involving in situ diagnostics and ex situ characterization along with process maps provides a framework to describe coating formation mechanisms, process parametrics and microstructure description.
Keywordscurvature measurements elastic properties stress evolution suspension plasma spray thermal cycling
This work was supported in part by the National Science Foundation—Partnership for Innovation (NSF-PFI Grant No. IIP-1114205) and The Consortium for Thermal Spray Technology of Stony Brook University. The authors appreciate the Oerlikon Metco Team: Jose Colmenares-Angulo, Riston Rocchio-Heller, Jing Liu, Jonathan Gutleber, Ronald Molz, David Hawley, Montia Nestler, Michael Tobin and Richard Schmid for the help and support in setting up a suspension spray system at Stony Brook.
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