Metal Troubles - How to Prevent Galling

"I coated the 4340HTSR (with carbon nitriding) and also use some lubricant in between."

So, you have coated it, and lubricated already, but have not tested the new setup yet? Sounds to me like you have already made the decision, the best way to see if it is substantial enough to work is a good old fashion test. There are more exact sciences involved if you were still in the planning stage, but from your wording it sounds like you ought to just give it a go.

I can still change my design.

What are the sciences for galling prevention?

Many thanks

You'll need to know things such as the coefficient of friction of the two materials, the force which the materials oppose each other with, the speed the materials are moving against each other, I'm sure there are a couple other variables to be concerned with, but I'm about 15 minutes from being on vacation, and have already checked out.

Good luck,

See y'all in a week or so.

All good posts above. My 2 cents are:

- Heat treatment of parts (hardness and depth)

- Type of sliding (bearing pressure and duration)

- Dry vs. lubricated sliding surface

- Expected life of part (you cannot eliminate wear, only reduce it)

My experience is limited to engineered chain component wear. Galling and micro welding are usually the result of high bearing pressures and relatively soft materials. In general, heat treating of both parts will reduce wear with respect to time. How much and type will depend on how much you are willing to spend. You can through-harden, carburize, and induction heat treat depending size of material and depth of hardening you want to achieve. One drawback is hardening will also make a material brittle.

http://www.gordonengland.co.uk/

Google "Tribology" as there is a wealth of information out there on this subject. Tribology is the science and technology of interacting surfaces in relative motion in the presence of a third component (typically, the lubricant).

Another option to perhaps explore, cryogenic treating may help the galling problem, the "grain structure" of the steel is realigned, retained austinite converted to martinsite, causing the steel to be more resistant to wear. HOWEVER, any potential benefit would only accrue to the 4340 and more than likely not the 350W account of the carbon content of the material. .4% or greater Carbon is required for any strengthening benefit, the 4340 is right at that level, the 350W simply does not have a high enough carbon content. Anyway, just my input. dkimmel@300below.com