The relationship between chromium nitride and secondary austenite precipitation in duplex stainless steels

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 34; no. 8; pp. 1575 - 1597
• Main Authors: RAMIREZ, A. J, LIPPOLD, J. C, BRANDI, S. D
• Format: Journal Article
• Language: English
• Published: New York, NY Springer 01-08-2003; Springer Nature B.V
• Subjects: Alloys; Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Metallurgy; Metals. Metallurgy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Precipitation; Solid-phase precipitation; Steel; Austenitic stainless steel; Scanning electron microscopy; Phase diagrams; Chromium nitrides; Electron diffraction; Experimental study; Precipitates; Phase transitions; Precipitation; Stainless steel-304; Austenite; Phase equilibria; Steels; Microstructure
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-003-0304-9

A detailed investigation of the early stages of secondary austenite precipitation in five duplex stainless steel (DSS) commercial alloys (UNS S32304, S32205, S32550, S32750, and S32760) has been conducted using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Based on this study, a model is proposed that describes the interaction between Cr^sub 2^N and austenite (intergranular and intragranular) precipitation in these alloys. Depending on nitrogen availability and interface mobility, Cr^sub 2^N precipitation along existing ferrire/austenite interfaces precedes intergranular secondary austenite growth. The low-energy interfaces formed between the Cr^sub 2^N, the ferrite, and the austenite, along with the coupled diffusion processes, are the factors controlling this phase transformation. Finally, in the case of the intragranular nitrides, a mechanism is proposed whereby the nitrides serve as sites for heterogeneous nucleation of intragranular secondary austenite. [PUBLICATION ABSTRACT]