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3825 |
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Building a high temperature corrosion and erosion model for thermal spray coatings |
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Jarkko Metsäjoki* / VTT Technical Research Centre of Finland, Finland Maria Oksa / VTT Technical Research Centre of Finland, Finland Karri Penttilä/ VTT Technical Research Centre of Finland, Finland Jukka Vaari/ VTT Technical Research Centre of Finland, Finland Anssi Laukkanen/ VTT Technical Research Centre of Finland, Finland |
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A model is being built in order to better understand and predict high temperature corrosion and erosion properties of thermal spray coatings and materials in general. The model combines molecular dynamics simulation (MDS), constrained free energy method (CFE) and structural modelling with finite element methods (FEM). MDS tells about diffusion kinetics, CFE about the reactions that occur and the FEM model determines the structure and erosion behaviour as lamellae, lamellae boundaries, porosity etc. have different properties. Experimental data on oxidation behaviour and mechanical properties were obtained to validate the model. For oxidation behaviour, surface polished bulk materials and thermal sprayed coatings were exposed to various temperatures and exposure lengths. Oxidation depth and possible diffusion were assessed by GDOES as well as cross sectional SEM studies. On the surface, colour optical microscopy, 3D profilometry and SEM+EDS were used to investigate grain/lamellae boundary oxidation difference to grains/lamellae. Mechanical properties such as hardness and Youngs modulus for the erosion side were obtained by indentation and rough model validation is done through high temperature erosion testing. Once finished, the model is predicted to aid in coating/material development and selection for demanding high temperature applications. |