Wear Resistant Weld Overlay 1

[lukerobert]

We have an opportunity to take on a project that requires weld overlay of a part that requires a wear resistant overlay. Basically, the part (4130) has a rectangular track in which a roller bearing rides back and forth (we will overlay the track). I've done a little research, and noticed that Inconel 625 is sometimes used to hardface forging dies. We are comfortable with welding 625, so it would be nice if we could use it instead of experimenting with the many other hardfacing alloys out there.

Any opinions on using 625 as a wear resistant overlay for this metal to metal scenario?

 

[EdStainless]

625 facing is usually only used for hot work applications. It has good hot properties, but isn't nearly as hard as bearing surfaces.
Is there a reason that these tracks are not nitrided or treated with some other diffusion process?

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P.E. Metallurgy, Plymouth Tube

 

[tbuelna]

I would agree with EdStainless. Reworking the bearing track surface using a weld overlay of 625 Inconel does not seem like the best approach. The 625 Inconel material will likely gall from the bearing roller contact.

Have you considered machining the track in the 4130 part slightly oversize, hardening the track surface using gas nitride, and installing a new bearing with a slightly larger OD to match?

 

[metengr]

If you need a weld overlay, I would consider Stellite hardfacing.

 

[lukerobert]

We also weld Stellite 6 here but I think it would be too brittle for this application. I know there are several types of Stellite. Is there one that would suit this application better?

 

[lukerobert]

I will look into the gas nitriding also. The bearing track is part of a larger part that doesn't need to be nitrided. Is it possible to mask off the part and leave only the track area exposed to the nitriding?

There isn't a specific reason why these parts weren't nitrided to begin with. The parts (pipe tongs for drilling) we are looking at are 25 years old with some wear after many years of use. Customer wants to refurbish them. So, we could overlay with carbon steel,PWHT, machine to spec and then nitride. Would there be considerable dimensional change after nitriding? Or would it be best to have the machine shop perform a slight skim cut after nitridng?

 

[EdStainless]

If these are subject to impact then doing weld overlay with Stellite 6 and grinding back to dimension may be the easiest. Another option would be to look at using a metal spray process to deposit WC hardfacing (HVOF is common). Then you would grind that back also.

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P.E. Metallurgy, Plymouth Tube

 

[tbuelna]

"Is it possible to mask off the part and leave only the track area exposed to the nitriding?" Yes it is. You can use special paints or electroplating such as tin or copper to mask the part surfaces you don't want nitrided.

"Would there be considerable dimensional change after nitriding?" The gas nitriding is performed at temps below 1100degF, and since no quench is required there should be little distortion. There will be an extremely small dimensional change on the nitrided surfaces, but probably not enough to require finish grinding for your application.

With either nitriding or weld overlay, you will need to do some machining of the part. But to me it seems like less effort to machine the track groove oversize, nitride the part, and use an oversized roller follower.

Of course if the track groove will require periodic rework, you might consider modifying the part to accept a bolt-in track insert. This way it can be repaired quickly and likely at lower cost. Downtime is usually a major concern with machinery repairs, so this approach might be attractive to the equipment operator.