High carbon steel microsturture ething to highlight martensite on SEM - what etchant to use ?

[Karel Drasner]

Hi everyone, I am trying to etch a japanese shirogami knife steel to investigate martensite morphology. I have pretty good pictures on confocal optical microscope useing standard 1% nital but the surface is to flat for SEM. Best thing would be to desolve the retained austenite. Is there any etchant I could use to distinguish the 2 phases ? There are pictures of the microstructure on SEM and confocal. Thanks.¨

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The etch in the attached micrograph is not too bad; the problem is out-of-focus over most of the plane.
I would start with 1% nital (1% nitric acid in methanol). Alternatively, Villela's reagent. It frequently requires more than one attempt due to variable and unpredictable etching rates.

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