52100 Microstructural Questions
52100 Microstructural Questions
(OP)
The quick breakdown:
- 52100 Steel, through-hardened to a martensitic phase for bearings.
- Material from other sources with this part # are running fine, but this specific batch of material is growing/shrinking all over the place, going way out of round and out of flat.
- Cut and polished a sample, Nital Etched (5%) and here's what it looks like at 150x:
Doesn't look like the normal spiky pine-needles of martensite, that's for sure. I'm thinking that perhaps the dark areas are oversized spheres of Pearlite that didn't fully dissolve, but I'd love some other input. (Never was good at microstructures.)
For the record: It's cheap-ass Chinese Steel with questionable carbon smudges on the mill certification.
- 52100 Steel, through-hardened to a martensitic phase for bearings.
- Material from other sources with this part # are running fine, but this specific batch of material is growing/shrinking all over the place, going way out of round and out of flat.
- Cut and polished a sample, Nital Etched (5%) and here's what it looks like at 150x:
Doesn't look like the normal spiky pine-needles of martensite, that's for sure. I'm thinking that perhaps the dark areas are oversized spheres of Pearlite that didn't fully dissolve, but I'd love some other input. (Never was good at microstructures.)
For the record: It's cheap-ass Chinese Steel with questionable carbon smudges on the mill certification.





RE: 52100 Microstructural Questions
check chemistry.
You are right, this looks wrong.
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Plymouth Tube
RE: 52100 Microstructural Questions
RE: 52100 Microstructural Questions
ht
Here is the CCT diagram for 52100
ht
RE: 52100 Microstructural Questions
While it is easy to blame "cheap-ass Chinese Steel", it is quite possible the steel quality if just fine, but they just used a annealing cycle that resulted in a microstructure that is very difficult to austentitze. My experience with Chinese producers shows that they are not nearly as "cut every cost" conscious as domestic sources. They do often have quality issues, but if you are using them as a supplier, making the assumption that they are just trying to make it cheap can often make you overlook many of the issues that cause the problems. Then there is the whole language/culture issue...
rp
RE: 52100 Microstructural Questions
Polishing and etching the pre-HT samples shows bands of light/dark material in the microstructure.
RE: 52100 Microstructural Questions
The ideal microstructure for this steel should be carbides in a martensite matrix when heat treated. You should look at this structure at higher magnifications. ASTM A892 lets you rate the quality of the structure in terms of carbide size, network, and lamellarity by comparing structure at 1000X. Lower mag micrographs for this material are very misleading and subject to misinterpretation.
Aaron Tanzer
www.lehightesting.com