SS-Micro-structure Interpretation

[rifa92]

Hi,

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).

 

[EdStainless]

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

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P.E. Metallurgy, consulting work welcomed

 

[WKTaylor]

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

Regards, Wil Taylor
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[weldstan]

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?




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[blacksmith37]

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

 

[EdStainless]

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?

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P.E. Metallurgy, consulting work welcomed

 

[Dhurjati Sen]

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.

DHURJATI SEN

 

[karthik.kb028]

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


Regards By,
Karthik
Material Engineer

 

[EdStainless]

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

 

[Guest102023]

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?"

 

[replica]

What is the hardness?