troostite

[bubble13]

I am doing a hardening heat treatment on high carbon bearing steel.I have a problem of formation of a microstructure called troostite,which I observed it after tempering.How can I avoid this? Is it due to short austenitizing time (I am austenitizing at 850 C for 20 min)? Is there any reference where I can fetch information about this kind of microstructure ? Does this microstucture have any effect on mechanical property of the steel like fatigue properties( may be if it affects hardness or grain size)?

 

[redpicker]

Troostite is a (mostly) obsolete term refering to a tempered bainitc/peralitic mictostructure. It results from austentite not cooling rapidly enough to form martensite. Whether or not 20 min at 850 C is short or adequate depends much more information thay you have provided (such as steel chemistry, part size and configuration, furnace characteristics, etc...), so it would be difficult to say. Incomplete austentitzation can result in mixed microstructures in high carbon steels, though. So can inadequate quench.

And, such microstructures can adversely affect the properties, particularly bearing properties.

rp

 

[Robertmet]

"Troostite" should be avoided! There are a number of alloys in the high carbon bearing steel types - 52100 and similar. You may be able to find one that has the hardenability you need to avoid troostite.