Influence of Mo Additions on the Mechanical Properties of Cast Duplex Stainless Steels before and after Thermal Aging

Shilei Li,Xitao Wang,Yanli Wang

doi:10.3390/met9030295

Abstract

The influence of Mo additions on the mechanical properties of cast duplex stainless steel (CDSS) before and after thermal aging was investigated using a series of model alloys with different Mo contents ranging from 0 to 1.75 wt%. By increasing Mo content, the content, morphology, and distribution of ferrite in CDSS change significantly. After thermal aging at 400 °C for 3000 h, the impact properties of all CDSS specimens obviously decline, and their hardness values in ferrite significantly increase. The impact energies of the aged CDSS decline, and the proportion of cleavage features significantly increases with Mo content increasing. The spinodal decomposition kinetics in ferrite is not significantly affected by the Mo contents. High content and interconnected ferrite will lead to the severe embrittlement in CDSS after thermal aging.

Highlights

Cast duplex stainless steel (CDSS) components are widely used in the pressure boundary of primary coolant of light water reactors.These components have been found to be sensitive to thermal aging embrittlement at service temperatures [1,2]
It was found that the high content, long shape, and interconnection of the ferrite phases aggravated thermal aging embrittlement [8,9,10]
The microstructures in the four model alloys were observed in a Supra 55 (Zeiss, Oberkochen, Germany) scanning electron microscope (SEM) using the backscattered electron imaging (BEI) mode

Summary

Introduction

Cast duplex stainless steel (CDSS) components are widely used in the pressure boundary of primary coolant (i.e., the primary circuit piping and pump casing) of light water reactors. These components have been found to be sensitive to thermal aging embrittlement at service temperatures [1,2]. Ni, and Mo are the most important elements related to thermal aging embrittlement in CDSS, and they influence both the ferrite microstructure and spinodal decomposition kinetics

Methods

Results

Conclusion