Black smut after etched by Bechet and Beaujard solution

[Best99]

I found excessive of black smut and some pitting when observed with microscope after etching by Bechet and Beaujard solution at room temperature for 1 hr. My purpose is for observing prior-austenite grain size in quenched&tempered SUP9 spring steel.
Please suggest me how to fix this problem.

Thank you

 

[Hercules28]

Seems overetched. Reduce time. You can try masking half the sample to check different times.

Also you can use ultrasound to remove the smut.

Some etchants recommend the use of a boiling solution for the smut...Can't remember which one that is.

metallographic.com is a good resource.

 

[Hercules28]

Post a pic.

 

[TVP]

I agree, sounds overetched. Are you adding at least 0.5% sodium alkylsulfonate or another appropriate wetting agent? Several successive etching and polishing steps are sometimes necessary to ensure that sufficient contrast develops between the grain boundaries and the rest of the specimen.

 

[Best99]

For wetting agent, I used detergent for this purpose.

Thank you