Precipitates of nuclear grade 316NG austenitic stainless steel under thermal aging

doi:10.13251/j.issn.0254-6051.2023.11.008

Abstract

Abstract: Precipitation conditions of the 316NG austenitic stainless steel in the nuclear environment were studied by means of thermal aging simulation experiment, electrolytic extraction experiment and the CALPHAD method. Then, the thermodynamic database of the 316NG austenitic stainless steel was established by the CALPHAD method. The results show that the 316NG austenitic stainless steel has no precipitated phase during annealing at 450 ℃ for 100 h, the Cr₂₃C₆ is the main precipitated phase when annealed at 450 ℃ for 500 h, and the main precipitated phases are Z-CrNbN, Cr₂₃C₆ and Laves_C14 when annealed at 450 ℃ for 1000 h. Based on the thermodynamic database, at 450 ℃, the equilibrium precipitated phases calculated by the Thermo-Calc software are Cr₂₃C₆, Z-CrNbN, Laves_C14, Ni₃Si and MX, and the total atom fraction is 3.5%, among which the content of Ni₃Si and MX is only 0.46%. The calculated precipitated phases by CALPHAD are good agreement with the results by thermal aging experiment of annealing at 450 ℃ for 1000 h, showing that the more complete information is obtained on the precipitated phases and their compositions of the 316NG austenitic stainless steel under long-term thermal aging.

Key words: 316NG austenitic stainless steel, thermal aging, precipitates, CALPHAD

CLC Number:

TG161

Sui Kailun, Ouyang Jinfei, Gong Minghao, Hu Hongxing, Li Jiafeng, Yang Shan, Long Zhaohui, Li Xiaobo. Precipitates of nuclear grade 316NG austenitic stainless steel under thermal aging[J]. Heat Treatment of Metals, 2023, 48(11): 50-54.

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