H900 heat treatment of 13-8 stainless

[Sjscat]

Hi,

I am new to this forum, but I have a question about heat treating 13-8 stainless. I am used to H950 being used to heat treat 13-8. However, I saw a call out for heat treating 13-8 parts to H900. I know H900 is used to treat 17-4 stainless.

I suspect H900 treatment, instead of H950, would increase 13-8 parts a few hardness points. Is this true? What other effects on the metal would be seen? I have found no information in regard to this. Can someone comment please?

Thanks!

 

[EdStainless]

What are the parts used for?
(I ask because AMS has been updating aerospace specs to not allow any aging below 1000 except in some very special cases)
Both the 900 and 950 aging treatments will produce material with low ductility and high sensitivity to SCC and hydrogen embrittlement.
I presume that your material is VIM/VAR.
If you look at 17-4 data, you see a 2-point increase in H900 over H950.
However, all of the information that I have for 13-8 does not show data for H900.
The alloy is most commonly used in the H1000 (or higher) condition because of its very high toughness.


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

 

[Sjscat]

Thanks for your reply. This is for the medical device field. It is a piece which is diamond coated and is used to abrade teeth. There is a motorized device behind it which moved the metal tip. All of these tips eventually wear out, but it is desirable for the thin tips last as long as possible. The tips break or wear off all the plated abrasive.

I thought that all 13-8 was VAR?

 

[EdStainless]

If it is from a major US or EU source, yes it will be VIM/VAR.
But there are a lot of other sources in the world.
If I were you I would first double check with load thermocouples to see what your actual aging temp is.
I would then adjust my offsets to assure that I was running 940 +/-10F.
Have you considered Custom 465?

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

 

[Sjscat]

Hi,

Yes, the material is from a major US source. I will check the heat treatment firms CoA. We buy annealed, machine, bore and bend it. They we have it heat treated.
I had never heard of Custom 465. I will look into that.

Thanks!

 

[EdStainless]

Do you have the parts re-annealed as part of the HT?
If you don't you likely have a lot of variation of properties within the part because of the strains that you introduced,
I used to make a lot of 17-7PH tube.
For each new coil of strip we would take samples and HT in the lab to see if we needed to adjust the final HT.
It was often only by 10F, but it let us deliver nearly identical properties for every lot.

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

 

[WKTaylor]

S, Ed...

MMPDS-17 Section 2.6.6 PH13-8Mo... material specs listed...

AMS5934 Steel, Extra High Toughness, Corrosion-Resistant, Bars, Wire, Forgings, Rings, and Extrusions 13Cr - 8.0Ni - 2.2Mo - 1.1Al Vacuum Induction Plus Consumable Electrode Melted Solution Heat Treated, Precipitation-Hardenable - UNS S13800

AMS5629 Steel, Corrosion-Resistant, Bars, Wire, Forgings, Rings, and Extrusions 13Cr - 8.0Ni - 2.2Mo - 1.1Al Vacuum Induction Plus Consumable Electrode Melted Solution Heat Treated, Precipitation Hardenable - UNS S13800

For both the AMS5934 and AMS5629 processed material, condition H950 is the very highest strength level [lowest PHT temperature] listed.... but the following statement from MMPDS-17, [PH13-8Mo] 2.6.6.1 Comments and Properties is very important to 'read and heed'...

However, for tensile application where stress corrosion is a possibility, PH13-8Mo should be aged at the highest temperature compatible with strength requirements and at a temperature not lower than 1000 F for 4 hours minimum aging time.

Regards, Wil Taylor
o Trust - But Verify!
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", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[EdStainless]

We have been revising all of the HT specific product specs (ASM XXXX H1050) and for the ones below 1000F we have then been immediately stabilizing them.
This effectively puts them out of reach for new design work.
The only exceptions that I know of are for some spring wire applications (such as 17-7 in CH900).

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

 

[WKTaylor]

Ed... are You on the SAE/AMS committee(s)... or the MMPDS committee(s)... or both?

Regards, Wil Taylor
o Trust - But Verify!
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", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[EdStainless]

SAE/AMS E and F. The MMPDS rep attends those meetings.

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