Plasma spray insulation coating for ITER magnet supports

Summary form only given. In the ITER magnet system, low voltage insulation coating on the shear pin is required in both CC supports and TF supports. Based on the ITER design, the plasma spray Al₂O₃+3% TiO₂ coating with 0.3mm thickness should be developed. Because the coating withstands the strong shear force during operation, high adhesion with the matrix is expected. In this study, an advanced plasma spray system (developed by GTV, Germany) was applied. In order to increase the bonding, a 0.1mm thick NiAl alloy interface was prepared before the plasma spray, which can be clearly seen in the microstructure of the coating. The test result shows that the interface can improve the bonding strength of the coating with a matrix: without interface 33.4 MPa, with NiAl interface about 40MPa. Further thermal shock tests of the coated sample were carried out between 300K and 77 K for more than 50 times, no crack and debonding were found. The electrical resistance test shows that the resistance is 1.06×10¹⁰ Ωm after cycling load test, which can satisfy the ITER requirements. In addition, the shear pin with Al₂O₃+3% TiO₂ coating can be polished to very good conditions. However, further 120,000 cyclic shear loading test of the coating are still planned, a special test machine is set up in our lab, the result will be present soon.