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20CrMnTi

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edendebrock

edendebrock

Industrial
Aug 29, 2009
5
US
We have been getting gears made from this alloy. We are starting to see failure not on the gear teeth but on the bearing journals. In the past we have been using 8620 or 4320. Does anyone have any expreience with these different alloys. The application is for hydraulic pumps and motors.
We case harden and oil quench followed by -100 F treatment.
The case is .04 to .05 deep after grind. THe surface is 58 to 62 Rc
We do not have a microscope so, the observations are with reduced magnification. The surface seems to be flaking and there is a dullness to the area were the bearings roll.
We are using needle roller bearings.

 
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Sounds like surface fretting damage from a poor fit between the inner race and the shaft surface. Go back and find out what the interference fit was supposed to be for the inner race against the shaft from the bearing supplier.
 
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I agree with metengr. I am familiar with this alloy as a replacement for 8620 and 4320, and surface hardness is not a shortcoming, which would be the most likely material-related problem for bearing journal failure.
 
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I have checked with the bearing manufacturere (they are a US firm) and have measured the shaft diameter. The shaft is with in specifications for what the bearing company recommends. Could an overloading of the bearing have a simillar failure?
 
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