Microstructure Question
Microstructure Question
(OP)
I'm wondering what the process history is for the part that I have (attached). The material is either 1018 or 1022, and the vendor (China) claims that the part was carburized, quenched and tempered but I am not seeing this upon looking at the microstructure. The surface hardness is 35HRC and the core is around 33HRC. I'm clearly seeing pearlite and I'm assuming the white is ferrite. The sample was etched in 2% nital for 30 seconds, and the mag is 1000x. If I'm seeing pearlite and ferrite, how is it possible that the hardness is so high without heat treat? Extensive cold-drawing?





RE: Microstructure Question
How deep is the carbuirzed case?
How deep is the location of the photomicrograph?
1020 doesn't have much hardenability. Even in the case with 1% C, you can get a fair amount of pearlite formation during the transfer from the furnace to the quench. I suspect that is what has happened here. Do you have a microhardness tester? Can you test the hardnesses of the light and dark regions? That may give you a clue.
rp
RE: Microstructure Question
Aaron Tanzer
www.lehightesting.com
RE: Microstructure Question
I'm starting to think that RP might be right. It looks like pearlite and martensite. Ferrite and pearlite would not explain the high hardness values seen.
RE: Microstructure Question
RE: Microstructure Question
One standard definition and measurement for case hardening is the depth to which 50HRC minimum is attained. That is found nowhere on your sample, although you may have a product-specific requirement.
The structure looks to me more like ferrite + pearlite in a medium carbon steel.
Buy American would be my solution.
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Microstructure Question