| In the liquid LiPb self-cooling and magnetic confinement fusion reaction system, MHD pressure drop will be induced when liquid LiPb flows across high magnetic fields. This will increase power loss, reduce the operation efficiency of reactor, and increase the stress inside packet structural materials. The most effective method to reduce MHD pressure drop is to form an insulating coating on the structural wall.In this paper, Al2O3 insulating coating were prepared on 316L steel and a new kind of RAFM steel using APS method, spraying NiCrAl as bonding layer.The results show that Al2O3 coating on both steel consist ofα-Al2O3 andγ-Al2O3, and tissue of the coating is very dense, with coating on RAFM steel being more dense.Al2O3 coating on both steel present good thermal shock resistance and adhesion strength, and coating on RAFM steel shows better adhesion, for the reason that the thermal expansion coefficient of RAFM steel is much lower than 316L steel, and it matches better with Al2O3 ceramic.The room temperature resistivity of Al2O3 coating on both steel satisfies the preliminary designing requirements of fusion reaction system, and the resistivity of coating on RAFM steel is more than that on 316L steel.The high temperature oxidation resistance of RAFM steel has been enhanced greatly after spraying coating, and the value of Kp has been reduced by an order of magnitude. In the oxidation process, O element has been diffused constantly from the atmosphere to NiCrAl bonding layer, and most of Ni and a few of Cr in the bonding layer have been diffused to Al2O3 layer. What's more, most of Al and Cr have been oxided, but most of Ni still exists in the form of original state. |
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