galling problem; 52100 chrome steel sliding on A2 tool steel, 57 HRC

Posted by Penny ( on June 04, 2004 at 22:17:41:

My company is experiencing a problem with galling between a cam and cam follower. Can you make any suggestions for improvement?

The cam is A2 tool steel with a hardness of 60-61 Rockwell C and a surface roughness of 12 (Ra). (We wanted a 4 roughness but it wasn't achievable by our vendor).

The follower is 52100 chrome steel, 57-58 Rc, measured surface roughness of 4 Ra.

Lubricant is a lithium based grease with MolyDiSulfide and "polymers". There's no recirculation of the lubricant so I believe its effect is negligible after the first cycle. We have a reciprocating sliding motion.

Due to the loads in our application, we are forcing the material to deform til the contact area is sufficient to carry the load. The follower surface is spherical and we wear a small flat path in it.

Coatings we have tried wore off immediately. We cannot reduce the load, nor distribute it among more contact points. We get almost immediate galling on the larger units (and a terrible noise), then over time it wears in and carries the load.

We are considering methods to reduce the surface roughness, alternate lubricants, and a coating for the A2 element to try to break up the adhesive wear mechanism. Do any of these seem like a waste of time? Which avenue would you deem to be most promising? Any other ideas?

Your comments would be greatly appreciated.

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