| Liquid PbBi alloy is usually selected as a reactor coolant for the accelerator driven subcritical system(ADS) and lead-cooled fast neutron reactor(LFR).Becausematerials for piping and tanks in the loop and impeller of main pump, whichare mostly made of austenite stainless steel such as 316 L, are immersed in liquid PbBi all the time,the stream of high-velocity liquid PbBi may cause a series of issues, including the corrosion of structural materials and the deep impact on structural materials. The majority of the elements of Ni, Mo on the surface of stainless steel should dissolve into liquid PbBi. So the liquid metal is interfused by the impurity,whichwill increase the difficulty of disposal of the waste because Ni, Mo isnot the elements with the low activation. One of the solutions to mitigating the dissolution ofNi, Mo into liquid PbBi is that cladding a layer of the coating with excellent corrosion resistance on the surface of materials. Therefore, according to the research onthe corroded performances of the coating and 316 L in high-velocity liquid PbBi, it could applyexperimental data and theoretical guidance to mitigate the corroding process of materials in high-velocity liquid PbBi.It is little particle WC with high hardness disturbing homogeneously on the substrate with high strength and high toughness that should improve the corrosion resistance and the wear resistance of the coatings.So WC particle is selected as a reinforced phase of the coatings in this experiment. Referring the content and the effect of the elements in China Low Activation Martensitic steel(CLAM), the types and the content of CrWMn iron-based coatings is designed independently.Besides, common steel 316 L is used as raw material in 316 L corrosion experiment. CrWMn iron-based coating and 316 L are served as the object of this study and then the corroded experiments of the coatings and 316 L in liquid PbBiwere carried out with the use of the rotating corrosion test device designed by our team. Besides, the effect of the content of W and the relative flowing velocity(RFV)on the corrosion performance of the coatings in liquid PbBi was researched, and the effect of high-velocity liquid PbBi on the corrosion performance of 316 L was also analyzed.After about 1000 h exposure to liquid Pb Bi with different RFV(1.70m/s, 2.31m/s, 2.98m/s) at 550?, the oxidized corrosion and the dissolution of elements were observed on the surface of the coatings. A double layer oxide film was formed, which consisted of the loose and porous outer layer Fe3O4 and the dense inner layer FeCr2O4. When the RFV is over 2.31m/s, new phase(Fe0.6Cr0.4)2O3 has been created. In the short term, the faster the flowing velocity is, the thinner obviously the thickness of the outer layer is, but that of the inner layer and the depth of penetration of liquid PbBi are almost unchanged.After about 1000 h exposure to dynamic liquid PbBi at 550?, double oxide layers were all formed on the surface of the coatings with different addition of WC(2.45%, 3.73%, 5.33%, 7.99%, ?t, %). The phase of the outer layer is loose and porous Fe3O4, while the phase of the inner layer is dense FeCr2O4 and(Fe0.6Cr0.4)2O3. A little amount of WC is contained in the outer and inner layer. The more the content of WC is, the bigger the thickness of the outer layer is, the thinner that of the inner layer. When the content of WC is over 5.33%, the thickness of the outer layer becomes thinner while that of the inner layer has already increased. Moderate tungsten compound could strengthen the substrate of the coatings and increase distinctly the corrosion and wear resistance of the coatings.The corrosion experiment of 316 L steel in dynamic liquid PbBi with the conditions of different RFV,(2.62 m/s, 3.69 m/s, 4.77 m/s) at 550 ?for about 1500 h was carried out. The surface of 316 L is covered with many corrosion pits and some loose oxidized flakes. After corrosion, the dissolution of elements was observed, and double oxidized layers which consisted of the loose and porous outer layer Fe3O4 and the dense inner layer Fe Cr2O4 and(Fe0.6Cr0.4)2O3were formed on the surface of 316 L. With the increase of the RFV, the embossing appeares with a certain direction on the surface of 316 L steel, and the thickness of the outer layer deceases distinctly while that of the inner layer reduced slowly. The diffusion and the dissolution of Ni extend to partial 316 L substrate. The hardness of the outermost substrate is also influenced by the elemental diffusion and the impact of liquid PbBi, whose influence has an increased trendwith the RFVincreasing. |
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