Effect of heat treatment on the corrosion behavior of 347H stainless steel in molten nitrate salt

Abstract

Abstract: In this paper, a static molten salt immersion experiment is used to study the corrosion behavior of 347H stainless steel with different grain sizes in mixed nitrate molten salt (60%NaNO₃+40%KNO₃) at 565 ℃ for up to 120 h. The corrosion kinetic curve is drawn by the weight gain method, the surface corrosion products and phases of 347H stainless steel are studied, and the micro-area composition of the corroded surface is analyzed to explain the corrosion mechanism of 347H stainless steel in nitrate molten salt. The results show that the corrosion rate of 347H stainless steel whose grain size is adjusted by solution treatment decreases during molten salt corrosion, and the corrosion kinetics curve becomes a linear growth trend. Through XRD detection, the corrosion products of 347H stainless steel in molten nitrate salt are mainly Fe₂O₃ and a small amount of Fe₃O₄ and NaFeO₂. Fe₃O₄ has a compact structure, which can effectively reduce the corrosion of nitrate molten salt to the steel matrix, resulting in a decrease in the quality loss of 347H stainless steel in the later stage of corrosion. The results of corrosion product morphology and cross section thickness analysis show that the corrosion layer thickness of 347H stainless steel reaches the minimum of 0.661 μm when the grain size of the stainless steel reaches 7 after solution treatment at 1 160 ℃-1 h, and the corrosion resistance of 347H stainless steel in molten nitrate salt reaches the best.

Key words: heat treatment, 347H stainless steel, molten nitrate, corrosion behavior

CLC Number:

TG172

TANG Meng-lan, WANG Jun, LIU Tian-zeng, LI Jun-chen, FENG Li. Effect of heat treatment on the corrosion behavior of 347H stainless steel in molten nitrate salt[J]. Journal of Lanzhou University of Technology, 2021, 47(5): 1-9.

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