Anti-galling stainless w/ high strength

[geesaman.d]

Hello,

I am trying to upgrade a component that is currently electroless nickel-plated 4340, approx 160ksi ultimate strength to a corrosion-resistant / uncoated material.

It is essentially a tapered wedge collar connecting a ductile iron sleeve with female taper to a straight shaft with straight cylindrical contour. The shaft is generally low carbon steel or 304 or 316 stainless steel. The taper angle is considered "locking" so galling and strength are both critical properties.

17-4PH H1025 (CB7Cu-1) would be perfect except it has poor galling characteristics vs. 300 series stainless.

416 and Nitronic 60 are interesting but strength is much lower. 440C is stronger and good on 316 but poor on 304.

Looking for ideas, and cast grades are actually preferred.

Thanks, David

 

[EdStainless]

You can buy Nit 50 and 60 in cold worked conditions.
The most available is round bar.
Strength of >125ksi Yields and >145ksi UTS is available.

How much do you use? What would be an ideal bar size?
You might get someone to cold draw some bar for you. (I know a guy ..)

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P.E. Metallurgy, consulting work welcomed

 

[geesaman.d]

Hi Ed,

We have five sizes of this component, and the most popular size is 6.25" OD / 1.6 long / 3.5 ID. Section thickness is 1/2" or less. So that means 6.5" round bar and most of it ends up as chips. Our quantity is 150/year so by my quick check its well below mill run quantities.

I had added Nitronic to the list but I suspect the cost would be inappropriate unless it could be cast in near-net-shape. I wonder if casting + cold working is possible.

Since posting this, I'm considering if 416 hardened to condition T might get the job done.

 

[EdStainless]

If only 1/2" why take it out of round?
What is the shape?
Someone might be able to cold draw it for you, at least near-net?

The galling of 17-4PH1075 on 300SS isn't bad. It is worth considering.

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P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

Silver plating could be a good solution provided the collar isn't frequently disassembled as there is some wear of the coating during each cycle.

 

[geesaman.d]

Here are a couple of quick views. I wonder if it could be cold worked from a plate, assuming even 'minimal' tooling cost wouldn't kill my savings on this small project.

Tugboat, this piece only gets disassembled every few years at most, but it's the cost and lead time of nickel plated alloy steel that I'm trying to beat.

 

[EdStainless]

What if it was made as two pieces?
A thin wall cold worked tube and a flange cut from plate. Then welded together.
It make production more complex, but less machining.

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P.E. Metallurgy, consulting work welcomed

 

[MintJulep]

You can do electroless nickle yourself with a glass pot and a hot plate.

 

[EdStainless]

Mint, it takes a little more, but not much.
Clean, etch, Cu flash, EN (electroless), and bake.
You can even pick P levels depending on how hard you want it.
And you could EN plate just about thing, sometimes you have to use a different flash plate under it.

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P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

Turnaround time for electroless nickel is about a week at our closest shop. However, it is silver that I see as the preferred anti-galling treatment.

 

[EdStainless]

We used to buy very thin silver foil and use in assemblies where galling was an issue.
They used to silver plate aircraft bolts for gall resistance.

There are other options also.
Coating with MoS2 or WS2, either as dry film or in a grease works very well.
For long term use there are synthetic greases available (Kytox or LOX8) that are fantastic at suppressing galling also.

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P.E. Metallurgy, consulting work welcomed