Galling 17-4 2

[tapley]

I am trying to fix a design where galling has occurred between two parts made of 17-4SST (H1025). I am looking for strength similar to 17-4, but I would like to prevent the galling? I have looked at using Nitronic-60 with the 17-4 and I am totally open to completely changing the materials? Another possibility I thought of was using 410 and 17-4. The corrosion resistance and strength are the main objectives for the design.

 

[Metalguy]

Have you considered hardfacing one of the surfaces? Nitronic 60 doesn't have nearly the strength of 17-4 H1025.

 

[metengr]

If you can change one or both of the materials, how about Inconel 718? This material can be solution treated/aged for the desired strength level and has good corrosion resistance. I have seen it used as bolting material.

 

[unclesyd]

Take a look a look at Carpenter Gall-Tough SS as mating metal. It carries a fairly high UTS (145,000) at RT.
Look at the plain material not the Super

http://www.cartech.com

 

[Carburize]

The surface coating option is attractive because the changes you will have to make (and any product testing) will be minimized.

 

[tapley]

I am fairly new to this type of problem. What is hardfacing and where can I specs for the right callout? Is hardfacing the same as surface coating? Also, if I were to sacrifice some strength on one of the parts what are some other materials I can look at?

 

[israelkk]

tapley:

When you say galling has occurred between two parts made of 17-4SST (H1025) what exactly the case are they just rubbibg against each other or you are trying to press fit the two parts? Can you give more info?

 

[tapley]

The parts are rubbing together. No press fit. I have a data sheet on the Carpenter Gall-Tough SST and it looks promising. I still welcome any and all advice.

 

[tmschrader]

I imagine you have tried Tef gel and this was not the right
application.

Tef gel compound will not work as good if the parts are rubbing each other, but it does work on bolt threads

 

[Carburize]

Check out the options for plasma nitriding the surfaces which are in contact with each other.

 

[metman]

Nitriding is what I would also suggest and you probably will only have to nitride one component and might want to mask all surfaces except the mating surface in case you need to machine after nitiding on the masked surfaces.

I am not familiar with plasma nitriding which might be more appropriate for your application but there are also other nitriding processes such as gas nitriding which however is expensive because it requrires a long furnace cycle but if you have a quantity of parts it might prove to be cost effective. Additionally I think you can combine the gas nitriding process with the age hardening cycle of the 17-4.

Jesus is THE life,
Leonard

 

[israelkk]

Plasma nitriding of 17-4 is done to my best knowledge in a temperature higher than 1025F (I think 1150F). Therefore the strength and hardness beneath the "very thin" nitrided layer will be lower than the current.

 

[unclesyd]

If your are considering Nitriding 17/4 the only way to go is Liquid Nitriding such as the Kolene QPQ process. Get in touch with Kolene as there are shops all over that do the work.
Do not attempt the normal gas (furnace) nitriding process on 17/4.

http://www.kolene.com

 

[funnelguy]

You might want to contact Dicronite. They have a tungsten disulphide dry film lube that has been useful in very similar circumstances. I have no direct experience with the product and am simply passing along what I've been told.

http://www.dicronite.com/

 

[lostsheep]

Unclesyd

Why do you advise against the normal gas nitriding for 17-4? Is liquid nitriding far superior or does the gas nitriding have a negative impact on 17-4? We currently use a shallow case gas nitride to prevent galling on 17-4 in the DH1150 condition.

 

[unclesyd]

I have some private correspondence from ARMCO that shows there is considerable difference in the properties of liquid vs gas nitriding 17/4. This mainly in the wearing properties of the two processed material. It has also been our experience that we get much better service with liquid nitrided 17/4 vs Nitronic 60, both in the wear and galling properties , especially if we have occasional contact. We had several failures with gas nitrided 17/4 both from the nitriding process itself and the inservice application. Also we had another application using both liquid nitrided 303 SS and liquid nitrided 17/4 where we got excellent results. 303 SS doesn’t gas nitride very well.
I didn’t pursue the development of any processing specifications for gas nitriding 17/4 as the liquid process would satisfy all our requirements and at the time liquid nitriding was considerably cheaper with a much quicker turnaround for us.
As stated in previous posts I installed the first Nitronic 60 vs 17/4 (liquid nitrided) components in the late 60's and early 70's and all are still performing.