Influence of Fabrication Route and Copper Content on Nature and Kinetics of 475 °C‐ Embrittlement in Cu‐Containing Super Duplex Stainless Steels

Abstract

The influence of hot‐rolling, hot isostatic pressing (HIP), welding, as well as copper content on low temperature phase separations and 475 ˚C‐embrittlement was studied in copper‐containing super duplex stainless steels. To suppress the presence of any phase separations, the samples were solution annealed and quenched, and to study the kinetics and nature of phase transformations during fabrication, the samples were aged for a very short duration of 5 min at 475 ˚C. Atom probe tomography results of medium Cu aged samples revealed that the processes involving more plastic deformation such as hot rolling and HIP accelerated Cr and Fe phase separation and caused precipitation of Cu‐rich particles (CRPs) in the ferrite, resulting in significant toughness loss. In contrast, the weld did not show a high level of Fe and Cr phase separation or CRP precipitation, preserving its toughness after the short aging. The experiment and the inverse interdiffusion calculations revealed that raising the Cu content slowed down Fe and Cr phase separation but significantly increased the CRP number density and decreased the toughness of the HIPed material. Precipitation simulation of CPRs showed that the model must be modified based on each processing condition. We conclude that hot rolling and HIP accelerate 475 ˚C‐ embrittlement, which could not be prevented by raising the Cu content.This article is protected by copyright. All rights reserved.