Hi, It would be really good if someone could share their expertise of etching (etchant & method) to reveal the microstructure of austenitic grain boundaries of Medium Mn steels (0.3% C, 5-11%Mn) ?
Thank you
Hello Akhil
Did you try with NITAL (1-5 % HNO3)?
As I can see it is martensitic steel (accord. to Guillet). With NITAL you will reveal martensitic microstructure.
Primary austenitic grain you can try reveal by oxidation metod (see ASTM E 112 or ISO 643).
Good luck
Hi Belma
Thanks a lot for your answer. I have tried Nital, but it revealed only the martensitic structure as stated by you. I have also tried a mixture of Picric acid, a Wetting agent and HCl and etching was done around 80-90°C. This could partially reveal the austenitic grain boundaries for one composition and etchant attack was very severe (numerous black spots).
I am interested to try other etchants which could may be reveal in a better way. I have no idea about oxidation etching. Could you pls brief out that?
Dear Akhil Varghese,
It looks like you have already tried the modified version of Vilella’s Reagent (Vilella's reagent is generally used for revealing prior austenite grain boundaries in 9Cr-1Mo ferritic/martensitic steels).
Though I do not have hands-on experience about your problem in medium Mn steel, please see whether these papers/links are helpful (you may also contact Prof. Dierk Raabe of Max-Planck Institut, Dusseldorf:- https://www.researchgate.net/profile/Dierk_Raabe)
1) The effects of prior austenite grain boundaries and microstructural morphology on the impact toughness of intercritically annealed medium Mn steel, Jeongho Han et al., Acta Materialia 122 (2017)
https://www.researchgate.net/publication/308892256_The_effects_of_prior_austenite_grain_boundaries_and_microstructural_morphology_on_the_impact_toughness_of_intercritically_annealed_medium_Mn_steel
2) https://www.researchgate.net/publication/236527603_A_new_etching_route_for_revealing_the_austenite_grain_boundaries_in_an_114_Cr_precipitation_hardening_semi-austenitic_stainless_steel
3) please see the link if you have access:- https://vacaero.com/information-resources/metallography-with-george-vander-voort/1405-revealing-prior-austenite-grain-boundaries.html
4) Project Report/thesis:- please see the link if you have access:-
http://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1124&context=matesp
Best wishes
Article A new etching route for revealing the austenite grain bounda...
Article The effects of prior austenite grain boundaries and microstr...
Please see the paper whether it is helpful:-
"Revealing Prior-Austenite Grain Boundaries and Martensitic Structure of As-Quenched AISI 4140 steel Treated by Plasma Electrolysis", L. Cenk Kumruoglu and A. Özel, ACTA PHYSICA POLONICA A, Vol. 123 (2013), 404:-
please see the link if you have access:-
http://przyrbwn.icm.edu.pl/APP/PDF/123/a123z2p083.pdf
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