Metallurgy.

[Guest matt]

Hi All,

 

I'm hoping someone can help me out with a rather general question on the effects of rust/pitting on case hardened steel. Some steel items are case hardened,ie heat treated for strength for example some bolts,the rollers on gun mounts and some gun parts themselves. My question is what effect does rust pitting have on such parts? does it cause weakness and if restoring rusted parts which have been heat treated will sand blasting effect the heat treating?

 

Hope this makes sense to someone!

 

Matt.

[sirhc]

Matt,

Head treatment affects the microstructure of the metal, rust/corrosion and sand blasting only affect the surface. There shouldn't be a problem blasting clean a head treated part. Obviously if the corrosion is serious the the material will be weakened but the hardness of the base material won't change.

 

Chris

[Guest matt]

Thanks Chris,just what I needed 8-)

 

Matt.

[Adrian Barrell]

The only potential problem with a case hardened part as opposed to a through hardened is rust pits can promote spalling of the hard surface. It depends on how deep the case hardening penetrates and what the part is doing.

 

A good example is a cam follower. If the face is pitted, oil will be forced, under pressure of the cam, into the pits allowing the rest of the surface to be quicly eroded.

 

Adrian

[Mrs Hardyferret]

Also, the case hardened surface can start to flake from the original rust pit.

Careful with blast cleaning on hardened surfaces as it is used to stress relieve surfaces,

and might give you probs

 

 

Regards HF