Debris from carburized gear 3

[UCengno1]

A product we produce in specific configurations utilizes a splash lube planetary gearbox for speed reduction. The sun (nitralloy) and fixed ring gear (8620) are nitrided and the planets (9310) are carburized. In order to facilitate identification of lube refill we have recently added sightglasses which has led us to another discovery, significant dark colored debris in the gearbox. The debris is so dark and pervasive that it completely eliminated the usefulness of the sightglass.

We do not have wear related issues but this discoloration is very disconcerting to the customer and we have a competitive product that does not have this issue.

An analysis is in process but I am assuming the debris is worn carburize. I am also assuming that this has been an issue long before addition of the sightglass so I need to be careful to avoid solving one problem while creating another.

Am I correct in the assessment of the debris as a result of worn carburized layer?
Is there another wear issue that could generate the dark debris?
Would a completely nitrided set eliminate dimish the dark debris?

Trying to start down the right road from the begininning of an investigation. Thanks.

BCK

 

[UCengno1]

Sorry about the delay in response...

Appears that a vast majority of the debris was from the gear elements. The material breakdown indicated primarily 9310/4340 material content. The gears in use were actually 8620 so I assumed that the program misidentified the material as 9310, 8620 was not one of the standard options. Apparently the silver (Ag) content was misidentified in the preliminary assesment. It was actually aluminum which must be comming from the aluminum gearcase housing. The total non-magnetic (aluminum) content was a magnitude less than the magnetic media. The only (currently) unexplained material was some 400SS material that doesn't match up with any of the "known" materials in the unit.

Of course this was the easy part, now I need to figure out why a "broken in" unit is creating so much debris. We have the same problem with new units so it is a consistent problem. I was considering a couple paths,

1) Gear alignment (sun to planet to ring)
2) Gear tooth form modification

The unit is pretty noisy so either of these has potential. 1) is easier to try quickly. The tale continues....

 

[gearcutter]

UCengno1,

Thanks for the follow up.
Looks like it might be time to start a new thread over at the Gear & Pulley forum

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[UCengno1]

Good point! See you there.

BCK