Graphite erosion from cast iron

[smurali1]

Hello all,

We are using a Cast Iron housing which has a machined hole. We pump lubrication oil through this hole.

Will there be any erosion of graphite from the cast iron and will it get mixed with lubricating oil.

I have this doubt because, if we rub our finger over machined surface, the finger becomes blackish (graphite!).

YOur feedback please.

 

[unclesyd]

Normally this is not problem unless you have very high velocities through the passageway, witnessed by thousands of CI motor blocks and gear boxes in service.

For you information there is a process, graphitization, where the graphite is leached from the CI and redeposited. This happens normally in pure water streams and some steam condensate system.

 

[cloa]

Graphitization is the selective corrosion of the steel component of the cast iron so that the graphite is remaining matrix- the dimensions of the part don't change but the remaining material is weak and brittle. I suspect its machining oils trapped in surface porosity. It probably just needs a thorough clean.

 

[smurali1]

Hello Unclesyd,

I note your point on high velocities will lead to to leaching.

My concern still is why do we get blackish color when we rub our finger - even after washing!. Rubbing of finger does not apply much force

Thanks

SPM

 

[arunmrao]

The blackening is as a result of free carbon,the exposed graphite flake for a similar reason is considered as solid lubricant and used on sliding surfaces and on parts where lubrication may not be possible.