Nanosized Cr-N clustering in expanded austenite layer of low temperature plasma-nitrided Fe-35Ni-10Cr alloy. (May 2022)

• Record Type: Journal Article
• Authors: Xie, Yulin; Miyamoto, Goro; Furuhara, Tadashi
• Is Part Of: Scripta materialia. Number 213(2022)
• Publication Date: 2022-05
• Subjects: Spinodal decomposition -- Short-range ordering -- Surface modification -- Three-dimensional atom probe (3DAP) -- Expanded austenite; Materials -- Periodicals; Metallurgy -- Periodicals; Metalen; Legeringen; Materiaalkunde; Metals, metalworking and machinery industries; Metals; Electronic journals; 620.11
• DOI: 10.1016/j.scriptamat.2022.114637
• Languages: English
• ISSNs: 1359-6462

Abstract

Abstract: Expanded austenite (γN ) formed by low temperature nitriding of austenitic stainless steel is a N-enriched fcc containing Cr-N short range ordering, but no direct observation of Cr-N clustering has been reported. In the present study, the nanostructure of an Fe-35Ni-10Cr (at%) alloy plasma-nitrided at 673 K was investigated using transmission electron microscopy (TEM) and three-dimensional atom probe (3DAP) technique in this study. Nanosized Cr-N clusters were directly observed in the γN accompanied with strong streaks in selected area diffraction, obvious modulated structure in TEM and Cr-N rich regions observed by 3DAP. Thermodynamic calculations suggested that Cr-N clusters were formed by spinodal decomposition due to a strong Cr-N attractive interaction. The hardness of the γN layer was much higher than that of Fe-N austenite steel, which indicates that the hardness is not only due to nitrogen solid-solution hardening but also to a synergetic effect of the coexistence of Cr and N. Graphical abstract: Image, graphical abstract