Determination of Thermal Spray Coating Property with Curvature Measurements
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Gopal Dwivedi, Toshio Nakamura, and Sanjay Sampath (Submitted April 22, 2013; in revised form July 12, 2013) Real-time curvature measurement of a coating-substrate system during deposition has facilitated the monitoring of coating stresses and provided additional insights into thermal spray deposition mechanisms. However, the non-equilibrium state of coating formation along with harsh spray booth environment introduces complexity not only in data interpretation but also in the coating properties estimation. In this paper, a new procedure is proposed to estimate the elastic modulus of thermal sprayed ceramic coatings using in situ curvature and temperature measurements. In order to correlate the measurable parameters to coating elastic modulus, a systematic study is conducted to develop a suitable methodology. First, various finite element model analyses are carried out to formulate suitable relations between the measurements and elastic modulus. Subsequently, experiments are conducted to validate the procedure to estimate coating moduli. The results are compared with more accurate measurements obtained from post-deposition characterization technique under low temperature thermal cycles. The comparison suggests that the moduli estimated using the proposed procedure are in good agreements with those obtained from the post-deposition technique. Further, the nonlinear response of coatings are evaluated from the estimated moduli during deposition and cool down, which offer additional information on the characteristics of thermal spray coatings.
Keywords
atmospheric plasma spray, curvature measurements, elastic modulus, finite element simulation, nonlinear stress-strain relation, yttria-stabilized zirconia
1. Introduction Performance and reliability of thermal spray (TS) ceramic coatings are generally defined by their microstructures which are greatly influenced by feedstock and process conditions. At present, direct visual and detailed evaluations of a coating microstructure via conventional or advanced methods (e.g., image analysis or small angle neutron scattering, etc.) not only require a significant amount of time, but also are challenging to quantify and scale. An alternate method to assess or estimate the coating properties is through its mechanical responses, as they strongly correlate with a coatingÕs microstructure and This article is an invited paper selected from presentations at the 5th Asian Thermal Spray Conference (ATSC 2012) and has been expanded from the original presentation. ATSC 2012 was held at the Tsukuba International Congress Center, Ibaraki, Japan, November 26-28, 2012, and was organized by the Japan Thermal Spray Society and the Asian Thermal Spray Society. Gopal Dwivedi and Sanjay Sampath, Department of Materials Science and Engineering, Center for Thermal Spray Research, Stony Brook University, Stony Brook, NY 11794; and Toshio Nakamura, Department of Mechanical Engineering, Center for Thermal Spray Research, Stony Brook University, Stony Brook, NY 11794. Contact e-mail: [email protected].
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