Hard Faced Bearing for marine winch shaft?

[Ibreakstuffdigitally]

Our normal design practice for winch shafts is to fit stainless sleaves on alloy steel shafts. These sleaves then run in grease lubricated plain bronze bearings. Operating loads are low, upset loads, which have a very low chance of very infrequent occurance, are high and would take the 660 bronze to just under it's yield point. Speeds are very low, often just a few RPM.

All has worked well for years, even with occasional immersion of the system... provided alignment wasn't too bad and provided the customer doesn't ignore the grease fittings for too terribly long.

We are, however, looking into trying to reduce the complexity of the fabrication process, cut down on some bearing diameters and so forth.

Has anyone had success in using a corrosion resistant material for hardfacing 4140 or 4130 tube/pipe/shafting which might allow us to eliminate some components?

The coating would need to provide a barrier to sea water in order to work. We do typically run lip seals, so some protection would be aforded in terms of keeping grit, etc. out of the bearing, but it's always been safer for us to assume a dirty environment. Wear probably will be an issue.

Thanks in advance for any suggestions!

 

[unclesyd]

I've used Bearium Bronze on quit a number of deck winches on large shrimp boats with very good results. As you state lack of lubrication is an ongoing problem which is well covered by the Bearium alloys as they will hold up quite well running dry.

http://www.metaltek.com/divisions/southern-centrifugal.html

http://www.metaltek.com/alloy-guide/non-ferrous/bearing-bronze/

 

[tbuelna]

Ibreakstuffdigitally,

Thin dense chrome is commonly applied as a wear surface on ferrous shaft substrates. It is very hard, corrosion resistant, adheres well to alloy steel, and has low friction properties.

Just design your shaft with a journal area that is slightly larger in diameter than the adjacent shafting, and make sure that all external corners in the journal area to be plated are radiused. The plating tends to build up excessively on sharp corners, and the radiused edges will result in a smooth transition in plating thickness after grinding which will prevent flaking.

The as-plated coating will be thin (.0003 inch or less) so a journal grinding process is necessary prior to plating in order to control tolerances. The shaft should also undergo hydrogen embrittlement relief immediately after the plating.

Finally, a light finish grind operation on the plated journal surface will produce a smooth and accurate surface for your bearing.

In service, the plated shaft journal surface can be ground and re-plated as many times as necessary. But it should not be too often, since thin dense chrome is very durable.

Good luck.
Terry

 

[Ibreakstuffdigitally]

Thanks, I'll look into it!

 

[unclesyd]

A good one to checkout is HVOF applied WC/Co coating. this being use as replacement for electrolytic hard chrome in many applications. It is used extensively on the 41XX and 43XX alloys in critical applications.
Applications and finishing are very important so if you decide to try it make sure you have a capable shop and as you probably know the devil is in the details...

http://www.cts-inc.net/chrome_replacement.html.