Case Hardening and Case Depth Measurement

[Curtis317]

Not knowing a whole lot about case hardening and case depth I have some questions. Our engineering group wants to define a specific location to measure the case depth. My limited knowledge makes me wonder. If the whole part is case hardened would not the case depth be the same all the way around the part no matter what form it is?

 

[Jim Wynne]

Not knowing a whole lot about case hardening and case depth I have some questions. Our engineering group wants to define a specific location to measure the case depth. My limited knowledge makes me wonder. If the whole part is case hardened would not the case depth be the same all the way around the part no matter what form it is?

Not necessarily. Although selective case hardening is possible (hardening of a specific area of the part) it's more expensive than hardening the entire part. It sounds as though there is a specific area of concern on the part, and it wasn't considered cost-effective to do selective hardening.

 

[Ron Rompen]

The case depth will vary according to the geometry of the part, the thermal mass of the part in the area being measured, and any pre-hardening that was done due to machining or working.

It is an EXCELLENT idea to identify a specific area in which to measure the case depth; that way there is less possibility of disagreement between yourself and your customer (been there, done that, got the t-shirt).

 

[Curtis317]

The part is about 6 inches long and has a large lobe on it that is 2.5 inches in diameter. It also has a long section that is @ 3/4 inches in diameter. Based on the response so far it seems that their would be more case hardening on the 3/4 " sections than the 2.5 in (1 inch thick) section correct?

 

[Wes Bucey]

I was not aware that configuration of product had an effect on depth of case hardening (heating the metal in a carbon-containing gas.) Case hardening is frequently done on gears .

I was of the impression depth of carburization of the metal was strictly a function of time and temperature. The subsequent quenching process also figures into the degree of hardness of the surface.

Case hardening is normally performed on mild steel to provide a hard wear surface while maintaining the low core strength of the mild steel.

To my knowledge, only mild steels are case hardened (they can't be through-hardened.) It makes economic sense where only the surface of the product needs to be hard for wear purposes because the mild steel is easier [less expensive] to machine than high carbon steel which can be through-hardened.

For a more definitive answer, I would consult a qualified metallurgist.