One gearbox was rebuild due to oil leak. The gear was noticed with surface damaged all wound contact surface. What could be the root cause via the damaged surface feature attached?

Thanks, Kevin

XE03-West_Sprocket_GB-7-14-08.pdf (1,166 Kb, 95 downloads) pictures of gear

Kevin,

In looking at the images, it looks like you have a contamination issue or water getting into the oil. Water will make it tough for the oil to maintain a lube film, especially with the sliding action of worm gears. Also, verify the correct oil and viscosity is being used. Many gear oils are not good candidates for worm drives. The oil should contain fatty acids that have long chain molecules that provide the maximum protection from the sliding action of a worm gear. Correct viscosity is very important also. Check with the OEM or your lube vendor for verification.

Just my 2 cents,

Gary B

Can it not be a cavitation issue if you are pumping high viscosity oil at high gear speed?
Regards
Irshad Akhtar

It looks like used oil has too low viscosity. The wear shows a lack of lubrication.

I'm with Gary. This looks like water contamination. Water (and/or other contaminates) entered through possibly the lip seal or breather.

Is this washed down with a hose? Special seals and breather are available for washdown duty.

The oil leak may have been due to displacement of the oil by water.

Can you explain next mechanism after water contamination in the gearbox that lead to surface damage as attached? mechanical pitting or chemical corrosion..?

Our oil supplier classify it as pitting of the bronze wheel which typically is due to excess Hertzian stresses. Is his approach related to water contamination?

to_larry.jpg (88 Kb, 45 downloads) close-up

I am not a lubrication expert but I would imagine that contamination with water led to viscosity breakdown. Wear then proceeds very fast because of the steel worm on the much softer bronze wheel. More specifically, the lubricant is no longer able to maintain a film between the worm and wheel faces, allowing metal-metal contact.

Maybe John Winterton will correct me, but I think that part of the reason that the wheel is bronze is so that the worm will not wear and the wheel can be replaced. It may also have to do with heat from friction.

Kevin, I'm no lubrication expert but the brown sludge alone is telling me there was a lot of water in the oil, as was pointed out above.
I wish I could take macro photos like yours. They're very good.
Best regards
Joe Mc Cormack

The really thick brown sludge is most likely a mixture of oil, water and bronze.

The damage is too advanced to tell for sure what the root cause is. The lube can easily be checked by a competent lube lab for water content. Anything over 1% is cause for concern.