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Hardness vs Thickness

2004

Hi,

A plate spring(material c75/c67)of 0.6mm thickness is hardened to 47-51 HRC for a loading application. And an another plate spring of thickness 0.4mm (same as 0.6mm except the thickness) is used for the same application.what will be the hardness? whether we can maintain the same 47-51 HRC as the first one? Expecting your reply. Thank you.

Senthil Arasu
designengineer - Coimbatore, Tamilnadu, India

There should not be any difference in hardness between the part with 0.4 mm thickness and the part with 0.6 mm thickness when heat-treated in the same environment.

Toby Padfield
Automotive module supplier - Michigan
2004

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I agree with Mr. Padfield, but wanted to add a couple of comments. First, I hope you aren't using the Rockwell C test (150 kg with Brale indenter) because the parts are too thin to be tested on the Rockwell C scale. You will probably have to use a superficial hardness test and convert to Rockwell C. Check the hardness test chart and find the minimum thickness for the specimen you are testing.

Second, if you didn't have proper atmosphere control during heat treat, you may have de-carbed the parts, and that can affect your hardness readings, if you're taking hardness readings from the surface.

Steve Bizub
- St Louis, Missouri
2004