Details matter: stainless steels / by Eric Dacus

Stainless steel, specifically 17-4, 304 and 316 are all grades that get used in surgical instruments all the time. But these steels are all fairly similar and when put two flat surfaces of the same material are in close sliding contact or load there isa risk of galling. What’s galling? 

Galling usually refers to the adhesive wear and transfer of material between metallic surfaces in relative converging contact during sheet metal forming and other industrial operations.

A quick overview of stainless steels:

Image from: and

In a sliding-wear situation, a galling failure mode occurs first, followed by dimensional loss due to wear, which is, in turn, usually followed by corrosion. Galling is a severe form of adhesive wear that shows up as torn areas of the metal surface. Galling can be minimized by decreasing contact stresses or by the use of protective surface layers such as lubricants (where acceptable), weld overlays, platings, and nitrided or carburized surface treatments.

Review of Wear and Galling Characteristics of Stainless Steel (.pdf)

Its hard to anticipate all the ways an instrument can fail, and galling is not a fun one to find out after-the-fact. The trade off between wear resistance and corrosion resistance in medical devices is very difficult because the parts will be cleaned and sterilized multiple times a week for the life of the part, so corrosion resistance is not really a negotiable item. Wear resistance then has to be solved by dissimilar materials or coatings. The above .pdf is the most comprehensive resource I’ve found so far.