Study On The Preparation Of Al₂O₃-TiO₂ Multiphase Coating And Its Corrosion Resistance In Flowing LBE

The Accelerator Driven Sub-critical System?ADS?combines the accelerator with the reactor because of its relatively safe and flexible system,the strong transmutation capability,the good neutron economy,the higher support ratio,Nuclear energy utilization in the development process of the existence of inadequate fuel and nuclear waste post-processing and reactor safety and other issues one of the important ways.Lead-bismuth alloy?LBE?has become the main candidate material for scatter target material and coolant in ADS system because of its excellent thermal conductivity and neutron performance.However,there is a special extreme condition in the ADS system.The structural materials need to be subjected to high temperature and high neutron flux and are in direct contact with the high temperature flow lead bismuth alloy with strong erosion on the surface of the metal structure.Therefore,The protective coating with good thermal stability and corrosion resistance has important engineering significance.In this paper,composite powders were prepared by FeCr powder,FeAl powder and pure Ti powder.The Al₂O₃-TiO₂ multiphase coating was prepared by flame spraying and laser in situ reaction process on the surface of CLAM steel.The surface of the coating is flat,the organization is dense,there is no obvious defect exists,and the matrix has formed a good metallurgical combination.The LBE flowing corrosion experiment was carried out by using KYLIN-RT liquid lead bismuth rotation corrosion experiment device developed by FDS team of Institute of Nuclear Safety Technology,Chinese Academy of Sciences.The corrosion resistance of the coated samples in flowing LBE was characterized by optical microscopy?OM?,X-ray diffraction?XRD?,scanning electron microscopy?SEM?and energy dispersive spectrometer?EDS?.The main research results are as follows:The multiphase ceramic coating samples was exposed to LBE at500?for 1000 and 2000 h,the flow rate of liquid lead bismuth alloy was 0.3m/s,after corrrosion,the morphology of the coating surface as a whole before corrosion remains intact,the coating surface in flowing corrosion after long time no obvious scour marks.X ray diffraction analysis showed that the composition and phase composition of the coating surface after the high temperature LBE corrosion did not change obviously,and the phase composition was stable.SEM/EDS analysis results show that the coating with compact structure can effectively protect the substrate of CLAM steel corrosion into the lead bismuth alloy did not occur in the process of corrosion test;hardness test results show that the coating on the corrosion of long 2000h long after the hardness is1631-1723HV_0.2,still has high hardness.However,in the process of1000h and 2000h corrosion,the CLAM steel samples without coating protection will produce double oxide layer with the obvious oxidation corrosion phenomenon of the impurity oxygen in Pb-Bi alloy.The outer oxide layer structure is more loose Fe₃O₄ oxide rich Fe,internal oxidation layer is mainly FeCr₂O₄ Cr rich spinel,2000h corrosion of CLAM steel after surface generated within the oxide layer and the substrate interface will appear in the oxidation zone of cracking stripping?internal oxidation zone,IOZ?.