The curvature method applied to characterize thermal spray coatings analytical linear elastic analysis

Thermal spray is one of the most common deposition technologies in the industry of thick coatings. During deposition, thermal strain misfit between substrate and coating layers develops residual stresses. The deposition process layer-by-layer generates quenching and peening stress that balance through-thickness of the composite beam (coating/substrate) to produce a profile of residual stresses. Under linear elastic assumptions, an analytic multilayer analysis is presented in this study, aiming to calculate the stress profile after the deposition process and after cooling to room temperature. The model uses curvature-temperature data acquired during the in-situ monitoring of the deposition process. The typical sprayed substrate is a thin plate which bends due the occurrence of residual stresses. All thermal stresses produced during deposition due to heating or cooling of the composite are taken into account. For post-processing characterization, the composite beam can be subjected to a heat cycle (heating-cooling cycles) to obtain the curvature-temperature behavior that is dependent on the expansion properties of the materials, and their respective in-plane elastic moduli. An analytic analysis for this ex-situ experiment is presented to determine the properties of the coating material, specifically 1) in-plane elastic modulus and/or 2) the coefficient of thermal expansion (CTE). This is of high interested provided that in most cases, these properties are unknown for the coating material, or are highly dependent on the processing. The property values are obtained as temperature dependent. Finally, a sensitivity analysis is presented for the purpose of determining the optimum parameters to conduct curvature tests applied to coatings. The optimum coating thickness to substrate thickness is suggested based on the modulus ratios and CTE’s. The goal is to minimize relative errors in curvature-temperature data collection during the in-situ or ex-situ experiments. ; La proyecci´on t´ermica es una de las tecnolog´ıas de ...