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SS-Micro-structure Interpretation

SS-Micro-structure Interpretation

SS-Micro-structure Interpretation


Hope you guys are doing well. I have occurred a microstructure (pic attached) which appears to be resembling that of martensitic stainless steel, however, the composition of the material is telling a different story. I used OES for chemical analysis, the sample consists of C (0.129 wt%), Si (0.108wt%), Mn (0.702wt%), Cr(17.341wt%),Mo(0.992wt%),Ni(4.41wt%), Nb(0.1wt%) and Fe (balance).

RE: SS-Micro-structure Interpretation

Looks like a modified 441 to me.
More Ni for use in thicker sections perhaps?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: SS-Micro-structure Interpretation

WHAT SStl alloy/temper and specification is it supposed to be????

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

RE: SS-Micro-structure Interpretation

With that chemistry, why do you think it would not have a martensitic microstructure? And why would you not consider it a martensitic stainless steel?


RE: SS-Micro-structure Interpretation

Close to 17-4 PH with no copper ,or F 6 NM ; looks like a normal microstructure , depending on heat treat.

RE: SS-Micro-structure Interpretation

Did you bother with calculating a FN for the alloy? This is martensitic.
I am sure that with the Ni and C you have it is possible to quench and get a lot of retained austenite.
While this might be helpful in hot working or welding it will require some attention.
If you single temper you will likely end up with a bunch of un-tempered martensite (because it converted later).
I didn't try to calculate a Mf temp, but my gut feel is that it would colder than room temp.
My thought is quench, temper, chill, re-temper.
What HT was used on this sample?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: SS-Micro-structure Interpretation

The Ni content around 4% will not make the steel austenitic. It will only aid a little bit to increase the austenitic area. Had there been no Ni, you would have got almost a 100% martensitic structure. But this Ni could lead to some retained austenite as Ed has said or it could be ferrite. Rest are all martensite, typical needle like structure, quite coarse though, not the fine type.


RE: SS-Micro-structure Interpretation

Anybody have idea about 420 martensitic series microstructural ? how we can reduce carbide precipitation ?

Regards By,
Material Engineer

RE: SS-Micro-structure Interpretation

How thick is this section? What was the austenitizing temp? Quench media?
Give us some info here.

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P.E. Metallurgy, consulting work welcomed

RE: SS-Micro-structure Interpretation

The composition is consistent with martensitic SS.
Hard-core SS if you get my meaning.

p.s., nobody should be reporting major alloy analyses to three decimal places.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

RE: SS-Micro-structure Interpretation

What is the hardness?

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