The authoritative public forum
  for Metal Finishing since 1989
-----

Galling of 316L on 316L

I am currently working through a galling issue involving 316L on 316L parts. Because of my application, I am limited to only 316L and any coatings must be approved for medical implant. Does anyone have direct experience with the affects of surface finish, material hardness, or surface treatments to prevent galling on same material applications. Thanks in advance.

Ernest Quintanilha
- Norton, Massachusetts
2006

---

Since you can not harden 316L that is not an option. Surface finish will have very little to do with it. Lightening the load and or speed will lessen the problem. I assume that lubrication of any kind is not possible. I think that you will have to look at chrome or electroless nickel plating the contact points. There is an outside possibility that you could use a hardened cobalt brush plating on one of the contact surfaces to solve the problem. Vapor deposition like titanium nitride might work, but it would tend to be expensive and I do not know how well it is accepted in the medical field.
What are you building?

James Watts
- Navarre, Florida
2006

Ernest, I have coated medical instruments with electroless nickel Teflon over stainless steel substrates with success. The surface coating was applied only to one of the matting components & solved a galling failure. The EN PTFE coating also passed a body toxicity test protocol.

Tim Deakin
North Tonawanda, New York
2006

---

2006

Why 316L? It is extremely galling-prone, and there are other suitable alloys for medical implants. Contact Carpenter Technologies re BioDur® implant alloys and other stainless and specialty alloys (free registration required): http://www.cartech.com/products/wr_products_stainless_medaloy.html

Austenitic stainless steels such as 316L can be plasma nitrided (aka. plasma-assisted ion nitrided) to greatly increase surface hardness without loss of corrosion resistance. It's done in a very low pressure at about 400 C, i.e., at lower pressure & temperature than conventional nitriding. It's been used on Ti-6Al-4V to minimize galling and wear in medical implants. Nitrogen-containing austenitic SS alloys are allowed for implants, so plasma nitrided 316L is likely allowed (but not positive).

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.