Effect of precipitates on hardening of 17-4PH martensitic stainless steel serviced at 300 °C in nuclear power plant

Abstract

When 17-4PH martensitic stainless steel serviced at 300 °C for long term in nuclear power plant, the thermal aging embrittlement and hardening will be significant. It will seriously affect the safety and economic operation of nuclear power plant. In this work, Three-Dimensional Atom Probe Technology (3DAPT) was used to characterize the element distribution, and the evolution of Cu-rich precipitate and Cr-rich precipitate with service time were analyzed. The results show that with the service time increasing, the number density and size of Cu-rich precipitate and Cr-rich precipitate in the material increase obviously, which leads to the increase of critical shear stress with dislocation. The main reason to hardening is the nucleation and growth of Cu-rich precipitates and Cr-rich precipitates, which the contribution of Cu-rich precipitates fits Russell-Brown model. The contribution of Cr-rich precipitates to hardening increases with the service time, and is greater than that of Cu-rich precipitates.