steel microstructure after heat treatment

[bearingsteel]

I have a roller that has been heat treated(quenched and tempered) and it has a strange microstructure. I think it's troostite but i don't know for sure.
It must be martensite with some small round carbides.

 

[CoryPad]

The magnification is a little low, but it looks like spheroid all carbides and blocky ferrite. Are you sure this was austenitized and quenched? It looks like the heat treatment was screwed up.

 

[metengr]

Is this a 52100 bearing steel? Also, I can see the carbides when I magnify the image but beyond this the image resolution is poor. What was the etchant and magnification?

 

[arunmrao]

I can see enough of carbides, and looks possibly 52100 grade steel. It would have helped,if steel chemistry, thermal processing details, magnification, micro hardness of various constituents provided for a more meaningful discussion.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[Metalhead97]

bearingsteel,

Please provided the steel composition (I'm guessing AISI 52100) and magification. All I can see are carbides and no contrast from individual grains. Thanks

MH

http://www.linkedin.com/pub/luke-autry/1b/510/566

 

[bearingsteel]

It's RUL(52100) steel and it has like 33-44 HRC. It must have 60 HRC. Something in heat treatment went wrong, i don't know what because i don't work in heat treatment. There are carbides but there is no martensite. The matrix looks like ferite or something else, troostite maybe, i don't know.

 

[metengr]

Agreed, most likely ferrite and carbides based on your hardness results.

 

[Metalhead97]

bearingsteel,

Is this a reconditioned roller or a new part? Do you know what condition the material was in before the heat treat cycle?

MH

http://www.linkedin.com/pub/luke-autry/1b/510/566

 

[arunmrao]

Were they oil quenched and the tempering temperature.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[bearingsteel]

It was annealed before second heat treatment and quenching in oil and tempering. Tempering was done at 180-190 degrees C.
It's a new part.
I just need to know what microstructure is this. Thx guys!

 

[CoryPad]

Spheroidal carbides plus blocky ferrite. Likely the quench was not correct and martensite was not formed.

 

[metengr]

Agreed. Or...the material did not achieve complete austenitization prior to quenching.

 

[arunmrao]

There might be a process delay during quenching or the thermocouples need to be replaced.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[bearingsteel]

Okay, thanks a lot.

 

[dbooker630]

Back in the day at the bearing plant where I worked we would do a Troostitic etch if underquenching was suspected. The polished sample was etched in picric to a straw-colored appearance, followed by a brief dip in nital and then rinsed. I don't know if you can get picric (my current employer won't allow me) but this might help. You mentioned annealing before second heat treatment - was there another heat treatment as Metalhead97 noted?

 

[Maui]

If he isn't familiar with heat treatment and can't tell what he's looking at under the microscope now, I would be very leery of advising him to handle something as dangerous as picric acid.

Maui

http://www.EngineeringMetallurgy.com

 

[dgallup]

When I was in college they moved the Chemistry department into a new building. During the move they discovered a drum of picric acid dating back to WWII. They had to evacuate the old chemistry building and surrounding buildings, cordon off part of campus and get the bomb squad to remove it. Not for amateurs.

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