4330v treatment for wear and corrosion 3

[acrmnsm]

We need a tough high yeild material approx 10" dia for some tooling. 17/4 ph was used previously but has had some failures.
4330V has been proposed but we think we might need to treat it post machining to increase wear/corrosion resitance. EG Gas Nitriding and steam tempering (oxidising)
What concerns me is that these treatments are carried out at temps are in the range of the tempering temperature.
EG Tata have offered us
ASTM E4330V 260mm dia
Normalise at 910c for 6 hrs air cool
Harden at 880c for 6 hrs Water quench
Temper at 590c for 12 hrs Air cool
Stress Relieve at 520 for 11 hrs Air cool
Giving 1100MPA Ys (162KSI)
-50 Charpy of 45

The Gas nitriding is at 460-560 for long times.
Steam tempering is 450-500 Not sure about the times yet.

Concern....

 

[CoryPad]

What do you want the nitriding compound layer thickness to be? You can produce approximately 10 micrometers in 2 hours on steel with the right setup, although salt bath nitriding usually works better. We do have gas nitrided parts (usually cast iron) that take up to 24 hours to produce 10 micrometers.

You are correct that you can have some tempering occur during nitriding. The standard procedure is for your temper/stress relief to be at or above the nitriding temperature.

 

[acrmnsm]

Its 3metres long, so we are having trouble finding a salt bath that big.

 

[CoryPad]

Yes, I understand your problem.

 

[EdStainless]

I would go with the gas nitride, maybe a at the lower end of the temp range.

What HT of 17-4 were you using and what were the failures? I would look at 13-8PH before you give up on PH SS.

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P.E. Metallurgy, Plymouth Tube

 

[MagBen]

I am with Ed, if HT properly, 17-4 can have both higher YS and impact stength than 4330, let alone its excellent corrosion resistance. Besides, it shows excellent resistance to oxidation up to 1100ºF,

 

[acrmnsm]

There are some other "reasons" to use 4330v, the 17/4 PH was H1025. (IE business reasons that are not relavant to a technical discussi0on and a bit annoying, plus at this stage I am not able to influence this, unless of course we finjd that there is not a suitable wear/corrsion treatment for 4330v...)
We currently want approx 100MPa yield with as high as possible charpy at lower temps. The 17/4 does not give as good charpy at this yield as the 4330V.

I guess I need to know will the proposed treatement method have a detrimental effect on the mech props of the underlying 4330v?
It seems that the Gas nitriding and the steam temper/oxidisng are at similar temps to the tempering and stress releif. If I push for them to be carried out at the lower end of the ranges, will we be ok?

 

[EdStainless]

If you can live with no corrosion resistance you might manage with 4330V.

The use of 13-8PH will give you much higher toughness. In the H1050 (of maybe even H1100) I would expect over 1000MPa Ys and -50 Charpy values that are higher than for 4330.

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P.E. Metallurgy, Plymouth Tube

 

[acrmnsm]

EdStainless, hence the requirement for a coating/treatment...

My question is really about the effect of the coating/treatment on the underlying properties of the 4330v, not a materials selection issue, at this stage.

 

[EdStainless]

None of your surface treatments will improve corrosion resistance, just wear resistance.

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P.E. Metallurgy, Plymouth Tube

 

[acrmnsm]

Our experience is that steam tempering produces an oxide layer on the surface that resists corrosion and helps to keep lubricants on the surface.

 

[MagBen]

162KSI, -50 Charpy of 45, was that for 4330v ?! That's amazing even it is 45J (vs ft.lbs) at that high level of YS.
Normally 17-4 is supposed to give a higher Charpy than 4330 at the same level of YS, let alone 13-8.
I am not recommending you, just a comment.

 

[EdStainless]

The steam tempering produces a tight adherent magnetite film that is good at resisting general atmospheric corrosion. If this will be in an aqueous environment then you need something much better.


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P.E. Metallurgy, Plymouth Tube

 

[WKTaylor]

RE 4330V or new generation PH13-8Mo high-fracture-toughness alloys...

Shot or laser-peen, followed by removal of surface roughness to a fine finish by light grinding + Titanium-Nitride [TiN] coating... or perhaps a flame-spray wear/corrosion resistance coating [cobalt (or) cr-Cobalt etc]?

What about one of the CRENS [nitrogen-surface-hardening CRES] alloys now being used in bearings?

Regards, Wil Taylor

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o We believe to be true what we prefer to be true.
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[acrmnsm]

magben see here extracted from mats cert from Tata (spec here Link

Thanks for your advice everyone, I shall review this and get back to you.