2026-03-24 中国科学院 （CAS）
Full-chain research strategy: revealing thermokinetics of sigma phase formation for precision chromizing control (Image by NIMTE)
＜関連情報＞
- https://english.cas.cn/newsroom/research-news/202603/t20260325_1153722.shtml
- https://www.sciencedirect.com/science/article/abs/pii/S1359645426001941
意外な促進剤：ステンレス鋼のクロム化を促進するシグマ相の熱力学的役割 Unexpected promoter: Thermokinetic role of sigma phase in accelerating stainless steel chromizing
Kai Xu, Xiaofei Hu, Xue Wang, Ming Lou, Jibin Pu, Denis Music, Liping Wang, Keke Chang
Acta Materialia Available online: 7 March 2026
DOI:https://doi.org/10.1016/j.actamat.2026.122088
Abstract
Chromizing enhances surface protection in harsh environments, yet mechanisms for its material-dependent variability remain unclear. We studied the chromizing of 316 and 310S stainless steels (SS) to explain their divergent layer growth. Unanticipated sigma phase formation occurred exclusively in 316 SS during chromizing, yielding a layer almost three times thicker than 310S SS under identical conditions. Thermodynamic and deep potential molecular dynamics analyses revealed that Mo promotes sigma phase at 1000 °C while Mn suppresses it. Crucially, the coarse-grained sigma phase accelerates chromizing by inhibiting surface carbide growth (barrier to Cr diffusion). Subsequent nitriding transforms sigma phase into protective CrxN, thus eliminating concerns over its embrittlement effects in applications. Based on these thermokinetic insights, we propose a sigma phase manipulation strategy via elemental screening to accelerate chromizing and enhance material durability.
