I am designing a surgical instrument which will be impacted many times over its life cycle. We are trying to determine the best heat treating option for the steel (17-4 precipitation hardened) so that we maximize its usable life. Typically, we heat treat 17-4 to H900. However, I'm not sure that this gives us the best mechanical properties for something which will be impact loaded. I was thinking something more along the lines of H1075 or H1150-M. Both of those options have higher Charpy Impact values, but both also have lower ultimate tensile strengths. We've had one device fail already (it was treated to H900). Any help would be appreciated. Thanks!