| CHEN Weiqian,LA Peiqing,XU Shipeng,MA Chao,LI Yaming.Effect of Heat Treatment on Microstructure and Corrosion Resistance of the Fe-Al Layer in Molten Chloride Salt[J],54(2):148-160 |
| Effect of Heat Treatment on Microstructure and Corrosion Resistance of the Fe-Al Layer in Molten Chloride Salt |
| Received:March 09, 2024 Revised:May 24, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2025.02.012 |
| KeyWord:310S stainless steel Fe-Al aluminide coating pack cementation thermal diffusion treatment chloride corrosion |
| Author | Institution |
| CHEN Weiqian |
State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metal, Lanzhou University of Technology, Lanzhou , China;Gansu Key Laboratory of Solar Power System, Jiuquan Vocational Technical College, Gansu Jiuquan , China |
| LA Peiqing |
State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metal, Lanzhou University of Technology, Lanzhou , China |
| XU Shipeng |
State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metal, Lanzhou University of Technology, Lanzhou , China;Gansu Key Laboratory of Solar Power System, Jiuquan Vocational Technical College, Gansu Jiuquan , China |
| MA Chao |
State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metal, Lanzhou University of Technology, Lanzhou , China;Gansu Key Laboratory of Solar Power System, Jiuquan Vocational Technical College, Gansu Jiuquan , China |
| LI Yaming |
State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metal, Lanzhou University of Technology, Lanzhou , China;Gansu Key Laboratory of Solar Power System, Jiuquan Vocational Technical College, Gansu Jiuquan , China |
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| Abstract: |
| The work aims to explore the effect of thermal diffusion treatment temperature on the microstructure of the Fe-Al aluminide coating, study its corrosion resistance in molten chloride salt, and provide a technical scheme for the application of 310S stainless steel in the field of chloride salt heat storage for photothermal power generation. The aluminide coating was prepared on the surface of 310S steel by pack cementation with a mass percentage of 77% Al2O3+20%Al+3%AlCl3 penetrant, and then it was treated by thermal diffusion for 30 h at 750-950 ℃ to improve the structure and phase composition and soaked in ternary eutectic molten chloride salt of 24.5% NaCl + 20.5% KCl + 54% MgCl2 for 30 h at 800 ℃. The effect of different thermal diffusion treatment temperatures on the corrosion resistance of aluminized coating was evaluated by static corrosion test. The microstructure, phase composition, cross-section morphology and element distribution of the coating before and after corrosion were analyzed by XRD, SEM and EDS. The section hardness of the coating was measured by microhardness tester. The aluminized coating was prepared by pack cementation for 15 h at 800 ℃ on the surface of 310S steel and its thickness was about 140 μm. The structure and phase composition of the aluminized layer were greatly affected by different temperatures of thermal diffusion treatment. The structure and composition of the aluminide coating under 800 ℃ thermal diffusion treatment were not changed. The structure of the coating was divided into outer layer and transient layer, which was mainly composed of Fe2Al5 phase at outer layer and FeAl phase at transient layer. The continuous oxide layer on the surface of the aluminized coating was not formed after corrosion in molten salt, and it was poorly protective for matrix. A large number of irregular holes appeared in the middle layer of the aluminide coating by thermal treatment at 850 ℃. An Al2O3 layer with a thickness of about 15 μm was formed on the surface of the coating after corrosion, which played a certain role in protecting for aluminide coating. However, coherent cracks appeared at the interface of the oxide layer and the aluminide layer, leading to loose bonding and easy falling. The phases of the aluminide coating treated at 900 ℃ were fully transformed into FeAl phase, and the interdiffusion zone with a thickness of 30.4 μm was formed at the interface of the matrix and coating, which enhanced the interface bonding force between the coating and the matrix. After corrosion, an Al2O3 layer with a thickness of about 32 μm was formed on the surface of the coating, and there were no cracks and holes in the interface of the coating and the oxide layer, and the better combination was achieved, which showed the best corrosion resistance. On the surface of the aluminide coating treated at 950 ℃, oxide layer was not formed after corrosion, and the corrosion depth of the aluminide coating along the grain boundary was about 54 μm, which showed poorer corrosion resistance. However, the surface of the aluminide coating on the 310S steel thermally treated at 900 ℃ in molten chloride salt showed best corrosion resistance, due to the formation of a dense and continuous Al2O3 layer in the corrosion environment. |
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