hello, please it's extremely urgent
i did this test f shot peening:
cast shot iron S330, hardness=490HV
target hardness 498HV
after that i measured the microhardness of the target i found that it decreas 460HV????????
can you explain that to me , i cant find any one for the moment it 's really strange!!!!!!
pleaaaaaaaaaaaaaaaaaase
and thank you very much

This really is unusual. Could you please state the nature, type and history of the target material?

Hello, I am new in shotpeening bussines, but I got information from Czech Material Research Institut, that some materials, which are hardened and carburized, can react on shotpeening like this.

Also my colleague in USA is material specialist for a long time and told me that he never saw that kind of reaction.

Does anyone else have similar experience?

Carburized and quenched steels are thermodynamically unstable. They are commonly tempered, which reduces, but does not remove, the instability. On peening, heat is generated together with massive plastic straining. This can induce "strain-accelerated tempering" which will result in a small amount of hardness loss.