Needles inside the ferrite in carbon steel

[Metalero]

Just to share this characterization of a piece of carbon steel with a surface finish, in which needles were precipitated inside the ferrite near the surface.
I am in the process of analyzing them in SEM to identify their qualitative composition.
Have you characterized any like that?

 

I've seen this before and it's fairly innocuous. I don't believe it is a precipitate, and I don't think SEM (EDS) will tell you much.
By 'surface finish' do you mean a coating or surface modification?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Metalero]

Yes ironic m., modification of the surface: at first glance it is black with small scattered brightness.

An article by Vander Voort shows similar ones that result from nitriding.

Anyway EDS could be useful (or not, it does not matter, it's in process).

 

[Metalero]

Confirmed: EDS in SEM show nitrogen in the needles and in some thicker precipitates in grain boundary next to diffusion zone.

(needles yes are precipitates: in theory Iron nitrides)

now i will analyze if they are inocuos or not for a good perfomance of the component.

 

The needles appear deep and uniform. If they are nitrides and not usually encountered, I might suspect deficient heat treating (though I am far from expert in that business).

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."