EBSD studies on phase transformation of ferrite to nickel free high nitrogen austenite by solution nitriding

International Conference on Applied Crystallography

October 17-19, 2016 Houston, USA

Mina Mohammadzadeh, Roghayeh Mohammadzadeh, Alireza Akbari and Marcel A J Somers

University of Tehran, Tehran, Iran
Azarbaijan Shahid Madani University, Iran
Sahand University of Technology, Iran

Posters & Accepted Abstracts: J Material Sci Eng

Abstract :

Solution nitriding is one of the cost-effective process and a novel heat treatment for producing nickel free high nitrogen austenitic stainless steels. For the purpose of fabricating these advanced austenitic stainless steels, it is necessary to obtain fundamental information on the ferrite to austenite phase transformation mechanism. In this study, the phase transformation of ferrite to nickel free high nitrogen austenite by solution nitriding was investigated using optical microscopy, X-ray diffraction (XRD) and electron back scattering diffraction (EBSD). Solution nitriding was carried out on a ferritic Fe-22.7Cr-2.4Mo stainless steel plates at 1200�°C for 1 and 3 h under nitrogen gas atmosphere of 0.25 MPa. The results showed that upon nitriding, the austenite phase with acicular morphology nucleated in the near surface areas and grew toward ferritic core. The depth of austenite layer was increased from 150 to 470 �¼m with increasing nitriding time from 1 to 3 h. The EBSD studies revealed that the austenite phase have Kurdjumove-Sachs (K-S) or Bain orientation relation with respect to the ferrite phase. The misorientation across ferrite/austenite phase boundary did not change by increasing the nitriding time. The austenite/austenite boundaries separated by high-angle grain boundaries with 50.9�° misorientation and there is large amount of twins of the type �£3 with 60�° misorientation inside austenite grains.

Biography :

Email: min.mohammadzadeh@gmail.com