Stainless Galling Between Nitronic 60 and 17-4 or 4140 1

[McCall920]

I'm in the process of doing a material analysis on some downhole products for the oil and gas industry. We thread the pieces of this component together, and it see's around 30ksi of pressure (which is balanced both inside and outside the tube). Our problem has been galling between these pieces of the assembly. Currently, we use 17-4 PH stainless due to its high yield strength and relatively good corrosion resistance in our application. Our problem is the thread galling between the two parts due to the stainless being the same material between the two mating surfaces.

My question concerns this Nitronic 60. Its great material for sure, has about the same yield strength as our current material at a level 3 HT. But its expensive stuff. I am curious though if I can use it on every other part, so that one thread is 17-4 and one is Nitronic. Will it have the same anti-galling properties, and not suffer from any galvanic corrosion (it has a short life so I wouldn't expect it), or other issues. 4140 would work as well in place of the 17-4, though its corrosion resistance is lower.

Part of the problem is we need a very tough material for the application. Occasionally these parts will see a one time stress of up to 100ksi (or higher in stress concentration areas). Therefore we can't use something like the Gall-Tough because its too weak.

Thanks.

 

[SJones]

thread330-317541


Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[mrfailure]

What antiseize (if any) are you using for this application?

Aaron Tanzer

http://www.lehightesting.com

 

[McCall920]

Thanks Steve, I saw that before, but wasn't sure how the temperature, pressure, and stress would effect my application.

Aaron, we currently use a proprietary grease that seems to be more of an assembly tool than anything. Doesn't make a lick of difference for galling at the stresses we're running.

 

[EdStainless]

Are you rolling or at least burnishing your threads? If not then start, using SS threads 'as cut' is asking for trouble.
There are real anti-size compounds. I have resorted to silver loaded Krytox grease in a pinch.

What HT condition is your 17-4PH?

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Plymouth Tube

 

[McCall920]

At the moment we use both an 1100 and an 1150 HT, depending on the model. And we do burnish the threads, but we are limited to cutting them. Its hard to roll interior threads, especially on some of our smaller tube products.

 

[McCall920]

Also, some of the anti-sieze is D.C. MP-50, some is G67 Molykote, some is G-N Metal Assembly Paste. None of them seem to work on 17-4 to 17-4. But keep in mind we are torquing these parts to a couple hundred foot pounds, and they are being assembled and disassembled multiple times by the customer.

I just can't get over how expensive Nitronic 60 is. The customer wants it, but doesn't want to pay for it...

 

[EdStainless]

We do tubing in Nit 40 (219). The only material available is double melted for aerospace applications. The price is stiff and availability is limited. The price is high for that.

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Plymouth Tube

 

[mrfailure]

There are some very effective heavy duty anti-seizes that may really do the trick. I have had good luck with Loctite (but do not disparage other brands by any means). I have attached a link to technical data sheets for their anti-seize compounds (Loctite does not make finding this information easy). As noted in another thread, make sure to avoid moly-disulfide anti-seize compounds.

Aaron Tanzer
www.lehightesting.com

 

[dgallup]

You can get cold-forming taps/ Search Emuge-Franken.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[aroundhere]

Yes, you can use 4140, 4130, 4340. The Rockwell C should be around 35 if you need a high yield. Not sure what kind of 17-4 you are using. I designed a 3.38 od tool that goes to 30,000 psi and not pressure balanced. Fun stuff. You also use 17-4 on all, but armoloy plate every other part. You can also copper plate the threads, but that is getting kind of old school because the copperplating today doesnt seem to hold up like it did 15 years ago. We use slikstuff on threads and oring. Works great for high pressures. I have heard that it can cause problems at very low pressures, but never seen it myself. Avoid V threads if possible and use stub acme. Most galling we have is guys taking apart or screwing together a long heavy tool horizontaly on a vice stand. THe weight of the tool hanging out there with the downforce just making the threads dig into each other. There should be another chain vice stand under the end of the free section, but people get in a hurry and stuff happens. anyway Good luck.

 

[aroundhere]

I just saw that your using h1150 17-4. and rolling threads, so disregard the thread info.