×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Problem with bearing structure

Problem with bearing structure

Problem with bearing structure

(OP)
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).

RE: Problem with bearing structure

What makes you think it went out with a martensitic structure? The easiest explanation is it did not; that particular bearing was improperly heat treated.

Aaron Tanzer
www.lehightesting.com

RE: Problem with bearing structure

(OP)
I know that theoretical it's possible if the bearing is overheated at about 900-1000 grades Celsius, it can be annealed. May this be the explanation?

RE: Problem with bearing structure

If the bearing is made from 52100 the incoming bar stock is typically spheroidized annealed. So another question to ask is whether the bearing was heat treated at all.

RE: Problem with bearing structure

It was never hardened to begin with. Assuming it was hardened, it is quite far fetched to suggest that over heating of the bearing caused it to spheroidize!

RE: Problem with bearing structure

I appreciate the word "theoretical" that bearingsteel used; I think in practice the bearing would have siezed long before it could have reached those temperatures.

Aaron Tanzer
www.lehightesting.com

RE: Problem with bearing structure

I concur, the bearing would have violently self-destructed before it could achieve a uniform annealed microstructure.

What kind of wear do you see?

RE: Problem with bearing structure

(OP)
I see that it has a half speroidizing structure and a half that it is almost quenched-tempered.

RE: Problem with bearing structure

I would hope you have a proper failure analysis performed and understand how the bearing performs in service instead of spoon feeding folks here information.

RE: Problem with bearing structure

(OP)
I don't think I can do this. I would like to see how it works and then fails thou.
I work in the metallographic laboratory so I must know also how they fail and how to resolve problems that arise.
Thanks anyway for your response.

RE: Problem with bearing structure

As metengr said, it is impossible to do a failure analysis based on fragmentary information (no pun intended).

Next bearings you supply, keep a control sample in your desk until such time as this customer returns a destroyed unit. Better yet, do some random sampling for hardness testing and metallography, a.k.a. QC.

RE: Problem with bearing structure

Many folks in metallography labs and are highly knowledgable in their specialties, but they are not specialists in failure. They hire labs with failure analysts because they understand how things fail, and it is more important to their organizations to gain this knowledge with assurance.

RE: Problem with bearing structure

As stated above, if heated to a temperature needed to create even a partially spheroidized microstructure, at temperature the bearing would not be able to support a load high enough to create the necessary friction and would disintegrate. A one to two week lifespan for a new bearing is typical of an improperly heat treated bearing. While this does not prove the problem in this case, it does explain the responses it has received.

From your limited description of the observed microstructure, I wonder if what you are seeing is a microstructure resulting from either too low of an austenitizing temperature or excessively high tempering temperature. While a metallogropher may not be the best failure analysist, a good metallographer should be able to recognize what thermo-mechanical history is needed to produce a given microstructure, given the steel chemistry and standard processing. There is a lot you can learn from from the microstructure, you should try to find out more from the manufacturing side what could have happened during processing as well as from the customer support side as far as what the application was. Correlate these with the clues seen in the microstructre and you will have a better understanding of what has happened.

rp

RE: Problem with bearing structure

Can you post a photomicrograph of the spheroidized structure and another of the quench-and-tempered area? Also a photograph of the bearing with arrows pointing to the noted structures would help.

RE: Problem with bearing structure

As stated several times, the bearing could not have reached spherodizing temperature before self destructing. Even if it were possible to reach that temperature in service, spherodizing requires extended time at temperature. It appears that heat treat was fouled to begin with. We surely would like to see the microstructure.

Design for RELIABILITY, manufacturability, and maintainability

RE: Problem with bearing structure

(OP)
So it's an interior ring with a half annealed and a half normalized structure(not quenched as i said earlier).
The half with annealed structure has 25-30 HRC, the other half has 40-45 HRC.

Here is the etched sample.


Annealed structure

Normalized structure

RE: Problem with bearing structure

(OP)
I'm very sorry. I did put 3 pictures in the reply but for some reason, it didn't appear. I will put them tomorrow, I have them on the computer at work.

RE: Problem with bearing structure

I was not able to view the web pages, they are blocked by my company server. Could you post them to Engineering.com? There should be a link on your Eng-Tips page.

RE: Problem with bearing structure

Those are interesting photos.

With the photomicrographs, it would help if you would identify the magnificaiton. I am also guessing, what you are calling "annealed structure" is taken from the right side of the "etched sample" and the "normalized structure" is from the right? The hardness of these two regions would also be enlightening.

What is the chemical composition of the steel? 52100 has been suggested, but my guess is that is only based that that is a common grade used in beraings. Do you know what the grade of steel is? Also, what is the overall size of the bearing? Is the bearing produced from bar stock? a forging? Do you know the perscribed heat treatment?

The left side of the "etched sample" appears to have multiple zones, much like what you would see with weld repair. As 52100 is not readialbe weldable, this does not make much sense, but that is the impression I get from looking at it.

We really need more information to provide much insight.

rp

RE: Problem with bearing structure

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

RE: Problem with bearing structure

(OP)
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

RE: Problem with bearing structure

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.

RE: Problem with bearing structure

(OP)
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?

RE: Problem with bearing structure

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

rp

RE: Problem with bearing structure

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.

RE: Problem with bearing structure

(OP)
I uploaded some pictures from the inner ring. This is all that we got for analyse.
http://files.engineering.com/getfile.aspx?folder=8...
http://files.engineering.com/getfile.aspx?folder=8...
http://files.engineering.com/getfile.aspx?folder=c...
http://files.engineering.com/getfile.aspx?folder=f...
http://files.engineering.com/getfile.aspx?folder=a...

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.


RE: Problem with bearing structure

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.

RE: Problem with bearing structure

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?"

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources