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Aging Precipitation Behavior of 316LN + Nb SS at 750 °C and Its Influences on Intergranular Corrosion Resistance
Author(s) -
Peng Xinyuan,
Zhou Xianliang,
Ye Zhiguo,
Dong Yinghu
Publication year - 2018
Publication title -
steel research international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.603
H-Index - 49
eISSN - 1869-344X
pISSN - 1611-3683
DOI - 10.1002/srin.201800087
Subject(s) - materials science , precipitation , intergranular corrosion , nucleation , phase (matter) , transmission electron microscopy , scanning electron microscope , metallurgy , austenite , microstructure , corrosion , analytical chemistry (journal) , composite material , chemistry , nanotechnology , physics , organic chemistry , chromatography , meteorology
The precipitation behavior of Nb‐containing 316LN stainless steel with different aging time at 750 °C are investigated by scanning electron microscope and transmission electron microscope. The degree of sensitization (DOS) of aged Nb‐containing 316LN SS to intergranular corrosion (IGC) are determined by double loop electrochemical potentiodynamic reactivation (DL‐EPR) technique. The precipitation sequence and the preferred nucleation sites for secondary precipitates (Z‐phase, χ‐phase, η‐phase, σ‐phase, M 23 C 6 ) are summarized. Z‐phase is the priority phase in Nb‐containing 316LN SS, and it precipitates uniformly in austenite matrix. Therefore, Z‐phase has no observable effect on IGC due to the absence of Cr‐depleted regions along grain boundaries. With Nb element addition, the precipitates of χ‐phase, η‐phase, and σ‐phase are accelerated, while M 23 C 6 incubation time is significantly delayed relative to Nb free SS. The DOS increases considerably with increasing aging time and no self‐healing process be observed even after aging for 1000 h, which is well consistent with the increase trend of precipitates.