5-8 September 2022
Wyndham Grand Salzburg Conference Center
Europe/Vienna timezone

Abnormal plate type iron-carbonitrides development during salt bath nitrocarburizing of Fe-4wt.%V alloy

7 Sep 2022, 18:05
Wyndham Grand Salzburg Conference Center

Wyndham Grand Salzburg Conference Center

Fanny-von-Lehnert-Straße 7, 5020 Salzburg, Austria
Poster Thermomechanical treatments Poster


Ms Anupama KASHYAP (IIT Roorkee)


A precise understanding of compound layer growth on nitrocarburized steels requires fundamental investigations on nitrocarburizing of iron-based binary and ternary alloys. Such studies were extensively carried out for the case of nitriding. To this end, this study is devoted to understanding the role of V on the structure and morphology of iron-carbonitrides developed during salt bath nitrocarburizing of pure Fe and Fe-4 wt.% V alloy. Salt bath nitrocarburizing is carried out in a cyanate-based bath at 500oC and 560oC for nitriding times of 4h and 10h. Treated specimens were characterized using light and scanning electron microscopes, X-ray and Electron Back Scattered diffraction techniques, and microhardness measurements.
An unusual plate-type morphology of γ’ and ε phases growing into ferrite matrix was evidenced in the case of Fe-V alloy and usual layer type growth of compound layer occurred in a pure iron specimen. Interestingly, the ε nitride phase was developed first (i.e., present at larger depths from the specimen surface) followed by the γ’ which has been attributed to the role of C in stabilizing the ε phase and C is known to enrich at subsurface regions during nitrocarburizing. Developed nitrides and carbonitrides maintained a specific crystallographic orientation relationship with the ferrite matrix. XRD and hardness measurements indicated the development of VN precipitates in the ferrite matrix before the plate-type growth of iron nitrides and iron-carbonitrides. Such plate-type morphology of iron-nitrides developed in nitride Fe-Al, Fe-Si, and Fe-Mo was attributed to the difficulty in alloying element partitioning required for the development of nitrides. In the current work where iron-carbonitrides were growing into a ferrite matrix in which all V has already precipitated as nitride suggests the role of developed VN and associated interfacial and misfit strain fields could be responsible for the unusual plate-type morphology. Thermo-Calc software and steels thermodynamic property database (TCFE9) were utilized to predict the phase constitution expected and were utilized to explain the observed phase formation sequence.

Speaker Country India
Register for the Tom Bell Young Author Award (TBYAA)? Yes

Primary author

Ms Anupama KASHYAP (IIT Roorkee)

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