Problem with bearing structure 1

[bearingsteel]

A bearing is sold to a customer and works good for 1-2 weeks, then it breaks.
When it came back, he has a different structure than it should have. A good structure is quenched(martensite) and it came back with an annealing structure(speroidised, fine globular cementite).
I want to know what would be the different causes of this(how did it happen).

 

[redpicker]

Another issue that may be worth looking into are the bearing installation procedures. Depending on the size and location, I would not put it past many of the maintenance men I have known to heat the bearing to assist in installation. Someone doing very agressive heating with an oxy-acetylene torch could to that to a perfectly good bearing is less time that it took me to type this response. Again, it's just a WAG, but if common installation procedures involve heating the bearing, it may be worth investigating.

rp

 

[bearingsteel]

The material from whitch the bearing is made is 52100. The heat treatment is supposed to be good for this bearing. It doesn't matter the temperatures. If it was quenched+tempered, it should had have a martensite structure.
Magnification of microscope pictures is x500 .
My guess is that it didn't go to the second heat treatment.
The half with annealed structure has 25-30 HRC, the other half(normalized) has 40-45 HRC.
The size of the bearing is 150 mm i think. The ring is forged, rolled, annealed and after this he must be quenched and tempered for hardening.


I put again the pictures for dbooker630.

sample Link
annealed Link
normalized Link

 

[mrfailure]

I question the heat treatment. Even if it is considered a "good" treatment, you still only get 45 HRC. I expect 52100 to have hardness values of at least 58 HRC. It is not enough to achieve a martensitic structure - you need a good carbide matrix throughout the structure. For that, I need to look at photomicrographs at 1000X and compare via ASTM A892.

 

[bearingsteel]

It's ok.
So i guess the second heat treatment was not done.
But what did happen to the ring that it has a half annealed structure and a half normalized?
It is possible that the ring was annealed and by working it reached high temperatures and normalized?

 

[redpicker]

In the picture you have identified as "sample", which half are you calling "annealed" and which half are you calling "normalized"?

rp

 

[dbooker630]

In addition to labeling the 'sample' photograph, can you also take a picture of the entire bearing, also with labels? Also show how the bearing is installed in the customer's product.

There is nothing we have seen at this point to suggest this bearing ever received a proper heat treatment, but as redpicker suggests, one side of the improperly heat treated bearing may have been heated for installation.

If in fact this part missed quench and temper you will need to review your lot traceability procedures, process flows, and control plans (if you have them). Something is wrong with material flow if green parts get to the customer.

 

[bearingsteel]

I uploaded some pictures from the inner ring. This is all that we got for analyse.

http://files.engineering.com/getfil...f245-4dca-96ec-3b97bebfef51&file=DSCN5282.JPG

http://files.engineering.com/getfil...54a9-4161-a2c5-1e724aa96b6a&file=DSCN5283.JPG

http://files.engineering.com/getfil...1ef7-49ad-a139-3edc5228ddaa&file=DSCN5284.JPG

http://files.engineering.com/getfil...d846-425e-9bbd-af02525bb3f4&file=DSCN5285.JPG

http://files.engineering.com/getfil...a50e-412e-9d53-a2d5de3788e8&file=DSCN5286.JPG

My colleague that has 25+ years of experience in metallurgy said that this ring was properly heat treated, but for some reason(maybe in service), it overheated, thus the annealed and normalized structure. Maybe it did behave like it was annealed in furnace, this is what I have to believe.

 

[mrfailure]

I feel like the cart is in front of the horse here and I would like to reiterate metengr's advice: With a bearing failure, you really need to first do a proper failure analysis. You will not be able to discuss whether microstructure occurred during failure until you define the failure itself. Looking at a cut inner raceway is not enough either. I find protocols for bearing failures to be amoung the most exacting - you have to look at everything (ncluding inner and outer races and balls/rollers) to understand what is going on. I also have always been able to identify failure root cause because the clues are always present when following an organized bearing failure procedure.

 

[Guest102023]

mrfailure,

And some FAILURE ANALYSTS in metallography labs should never have gotten in the business. Too many engineering overlords assume that because an appointed underling one has a degree or a PE they can excel at this kind of masochistic reverse engineering. Even within the field of 'metallurgical failure analysis' I find myself working within a surprisingly narrow range of industries.


"If you don't have time to do the job right the first time, when are you going to find time to repair it?"