Mechanical and Electrical Properties of Al₂O₃–TiO₂ Coating as Electrical Insulator

In a fusion reactor (i.e. ITER), the use of a ceramic coating on structural material (SS3I6LN-IG) has been considered as electrical insulator. Al₂O₃ including TiO₂ (Al₂O₃-TiO₂) is one of most promising materials as coating from a point of high electrical resistivity and so on. However, crack and peeling occur by difference of thermal expansion between substrate material and coating material. Therefore, 80Ni-20Cr was selected as the undercoating between SS316LN-IG substrate and Al₂O₃-TiO₂ coating. In this characterization, Al₂O₃-3%TiO₂ and Al₂O₃-13%TiO₂ were used as ceramic coating material. 80Ni-20Cr undercoating was fabricated by atmospheric plasma spray method. The thickness of 80Ni-20Cr was 50µm. Al₂O₃-3%TiO₂ and Al₂O₃-13%TiO₂ were fabricated by atmospheric plasma spray method. Thickness of these ceramic coatings are 200 and 500µm. From the results of out-of-pile test, it was clear that Al₂O₃-3%TiO₂ and Al₂O₃-13%TiO₂ coating had a good mechanical and electrical properties.