Some help: Aisi 316l with hardness approx. 250 brinell?

[Onoma Epwnymo]

Hello everybody. Please help me if you can with the following problem:

Today i made a chemical analysis on a hydrofoil's propeller shaft and the material was perfect match with aisi 316l.

The strange in the case is that the shaft's hardness was approx. 250 brinell, much higher than the standard hardness for this material, which is 180 brinell.

Can someone please explain to me how this shaft had such an elevated hardness (i measured the hardness at 10 different spots on the shaft's surface and the average was always 250 hb).

Looking forward for your explanations!

[Oilandgas]

316L stainless steel does not harden in response to heat treatments. It can be hardened by cold working, which can also result in increased strength.

The link below may help

[link Point to another website Only the registered members can access]