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6414 |
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Friday, June 12, 2020, Hall K2 12:00 PM Powders, Wires, Suspensions |
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Glass-bonded thermally sprayed ceramic coatings utilizing secondary raw materials |
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Marjaana Karhu* / VTT Technical Research Centre of Finland Ltd., Finland Juha Lagerbom / VTT Technical Research Centre of Finland Ltd, Finland Mari Honkanen/ Tampere University, Finland Jarkko Kiilakoski/ Tampere University, Finland Elina Huttunen-Saarivirta/ VTT Technical Research Centre of Finland Ltd, Finland Petri Vuoristo/ Tampere University, Finland |
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Agglomerated magnesium aluminate, MgAl2O4, spinel powders, for thermal spraying, were synthesized from secondary raw materials by spray drying and subsequent reaction sintering. Two secondary raw materials, talc ore mining tailings and aluminium hydroxide precipitate from aluminium anodizing process were studied. A stoichiometric pure MgAl2O4 spinel coating was prepared as a reference using commercial pure raw materials. Atmospheric plasma spraying (APS) resulted in the formation of ceramic coatings. Microstructural investigations revealed that secondary raw material based coatings contained amorphous areas between the crystalline MgAl2O4 clusters. The reference coatings exhibited crystalline lamellar microstructure of MgAl2O4, typical of APS sprayed coatings. The dielectric breakdown strength of the secondary coatings were at the same level, 24 V/µm, as compared to reference coating, 23 V/µm. Abrasive wear test results revealed considerably lower wear rate for the coating prepared from the experimental powders. As a main conclusion, these secondary raw materials could potentially substitute virgin raw materials in high-temperature electrical insulation ceramic coating applications. |