Heterogeneous Microstructure-Induced Creep Failure Responses in Various Sub-Zones of Modified 310S Welded Joints

Huaining Chen,Ying Kan,Yunlu Jiang

doi:10.3390/met12010116

Huaining Chen, Ying Kan + Show 1 more

Open Access

https://doi.org/10.3390/met12010116

Copy DOI

Abstract

In order to reveal the creep failure behavior of novel modified 310S austenite steel welded joints, the creep life and microstructure evolution of the 310S austenite steel welded joints were investigated in this study. The rupture life was assessed to estimate the damage of the welded joint based on creep rupture tests performed at 600 °C in the stress range of 170–238 MPa. Compared with WM, HAZ facilitated the occurrence of creep failure in long term creep due to the combination of a smaller hardness value, a more heterogenous microstructure accompanied by coarsened M23C6, a larger grain size, higher KAM and Schmid factor. Discontinuous Laves phases appeared near the boundaries between the δ-ferrite and γ-austenite grains in the WM, and dislocation strengthening and precipitation strengthening were observed near the boundary in the BM. Furthermore, segregation elements were detected by APT and EDS adjacent to the boundary. Cr and C segregation near grain boundaries weaken the creep resistance in long term creep service.

Highlights

AISI 310S austenitic stainless steel is one of the most promising materials for use in the key components of nuclear power plants or chemical industries, owing to its prominent comprehensive properties, such as excellent high temperature creep resistance and corrosion resistance [1,2]
Owing to the inherent microstructure heterogeneity, the 310S welded joints are subject to premature failure during creep service at elevated temperatures for long periods
In stainless steels subjected to elevated temperature, the precipitation of M23C6 and δ-phase particles is considered to be detrimental and can eventually cause cracking of the material [10,11]

Summary

Introduction

AISI 310S austenitic stainless steel is one of the most promising materials for use in the key components of nuclear power plants or chemical industries, owing to its prominent comprehensive properties, such as excellent high temperature creep resistance and corrosion resistance [1,2]. Owing to the inherent microstructure heterogeneity, the 310S welded joints are subject to premature failure during creep service at elevated temperatures for long periods. Due to the microstructure heterogeneity of welded joints, the creep failure behavior of welded joints under the service period should be of concern. A series of creep experiments were carried out on the welded joints at 600 ◦C and with a stress range of 238–170 MPa. The evolution of the heterogeneous microstructure was characterized in detail by using optical microscope (OM), scanning electron microscope (SEM), electron back-scattered diffraction (EBSD) and transmission electron microscope (TEM), which could be used to make clear the relation between failure location and crack behavior. Based on the creep resistance and microstructure characterization, the creep failure behavior of the sub-zones of the 310S welded joint was fully analyzed and clarified. Creep Experiment mm ×SS3ttaamnnddmaarrcddroccsrrsee-eesppecrrtuuioppnttuuarnreedss5pp0eemcciimmmeegnnassu,, gaaceccclooernrddgiitnnhgg, wttooertthheeeuAsAeSSdTTiMMn thEEi11s33s99tusstdtaaynn.ddTaahrredds,, pwweiicttihhmaae1n100s

Creep Experiment

FFrraaccttuurree LLooccaattiioonn and Morphology

Cracking and Failure Evolution WM

Microstructure Evolution durriinngg CCrreeeepp EExxppoossuurree

Findings

Conclusions