Preparation and Thermal Stress Analysis of Al $_{2}$ O $_{3}$ Insulation Coatings on SS-304 Tape

Al₂O₃ insulation coatings are grown on long-length stainless steel (SS) tapes using reel-to-reel sol-gel method for applications of HTS/LTS coils and magnets. Various ceramic solutions are prepared from Al based precursors, solvent and chelating agent, the coating are fabricated on SS substrates. Al₂O₃ solution was successfully obtained using Al-sec-butoxide precursor, and isopropanol and acetylacetone as solvent and chelating agents, respectively. In order to improve adhesion of Al₂O₃ on the SS-304 tapes, triethanolamine was used in the solution. The residual stresses are investigated at different temperature ranges, between (630, 600, 580, and 550degC) and room temperature for different thicknesses (12, 10 and 7 mum). The maximum stress values are obtained as 0.756 GPa as tension on substrate (SS) for the 12 mum coating and -1.0 GPa as compression for the 7 mum Al₂O₃ coating at 630degC . The surface morphology and microstructure of samples are characterized by a scanning electron microscope (SEM). SEM observation revealed that Al₂O₃ coatings have crack and mosaic structure.