Bearings/Bushing, Dry Film Lubrication, Grooving....

[shawnpeter]

The current bearing I'm dealing with is produced in house, and is made in a variety of sizes. The bearing is a multiple piece unit which incorporates a bushing, thrust washer, and a ball race (which retains our stationary peice to our peice in motion).

The bushing (kinda a misnomer, we just refer to it as the bushing) is a journal bearing, made from a Beryllium Copper alloy C17200 with about a 41HRc. We press this into the peice in motion with a .003" interference fit. We currently plate the bushing with silver .001" (+/-.0002") thick.

An example size of this bushing is 2.003" OD x 1.875" ID x .625" WIDTH.

What benefits/pitfalls would I have to doing a molybdenum disulfide or a polytetraflouroethylene dry film coating? Any suggestions?

Also, I've been playing around with the idea of adding a spiral groove to the ID of the bushing. Our system is lubricated with a propreitary degassed molybdenum grease.

Thanks!

 

[MikeHalloran]

What problem are you trying to solve?



Mike Halloran
Pembroke Pines, FL, USA

 

[romke]

both coatings can be effective under mixed or boundary lubrication regime. if you are able to achieve fluid film lubrication the coatings will have no effect

 

[ginsoakedboy]

As romke stated, once the fluid film is established the coating itself it not critical. I expect the coatings to influence performance during startups, shutdowns and dry-running spells. However, you should look into coating breakdown possibility within the range of operating temperatures.

 

[ginsoakedboy]

What would be the purpose of the spiral groove?

 

[shawnpeter]

my (probably incorrect) concept on adding a spiral groove to the bushing is that if cut and installed in the correct orientation it could be carrying grease upwards to the ball race and other components. yes/no?

 

[coatingengineer]

Hi.

Yes, in a "wet" boundary condition, neither MoS2 nor PTFE will serve you. Both function as dry film lubricants.

What problem are you trying to solve? Have you identified the mode of failure? Friction, itself, is a system-dependent parameter and function of load, velocity, temperature, surface finish, counter-face, material hardness, etc.

Grease tends to cold flow, displace under contact stress. To try and direct the grease, through spiral, at the right rate seems implausible. Not to mention depletion of lubricant.

You may want to see this link:

<a href="

http://www.industrialcoatingsworld.com/Low-Friction-Coatings/MoS2-Low-Friction-Coatings.html">MoS2

Low Friction Coatings</a>


William Gunnar

http://www.IndustrialCoatingsWorld.com

 

[MartinSr00]

I think spiral grooves are sometimes used in bearings and bushings as "dirt grooves" to allow dirt particles to escape the clearance before doing too much damage.

 

[romke]

grooves may be used in a bearing to direct the flow of oil or grease in a bearing. however, they should be very carefully designed in such a way that they do not constitute a path between a loaded and a unloaded zone of the bearing, otherwise you will not be able to get the hydrodynamical pressure buildup needed for proper lubrication.