Laves-phase evolution during aging in fine grained heat-affected zone of a tungsten-strengthened 9% Cr steel weldment

Xue Wang, Qiang Xu, Shu Min Yu, Hong Liu, Lei Hu, Yao Yao Ren

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

The precipitation and coarsening of Laves-phase in the fine grained heat-affected zone (FGHAZ) of a 9% Cr steel P92 welded joint during thermal aging at 923 K were investigated and compared to the base metal (BM), in order to clarify their effects on the Type IV fracture. Laves-phase precipitated mostly on the prior austenite grain boundaries of the FGHAZ. In comparison with BM, FGHAZ contained more grain boundary areas and can provide more nucleation sites for Laves-phase, resulting in an accelerated precipitation and rapidly reaching to the around 1.0% of saturated volume fraction. The coarsening of Laves-phase precipitates in FGHAZ was also much faster than that in BM, enhanced by the contribution of grain boundary diffusion resulted from its finer prior austenite grains. The FGHAZ had denser and smaller Laves-phase precipitates during the precipitation period in comparison with BM, obviously improved the creep strength by precipitation hardening. However, this effect in FGHAZ reduced sharply during coarsening owing to its coarsening rate greater than that of BM. In addition to the initial coarse polygonal subgrains with low dislocation density in FGHAZ produced by the weld thermal cycle and subsequent tempering in post-weld heat treatment (PWHT), coarse Laves-phase precipitates on grain boundaries formed in the long-term thermal aging, contributing to the formation of the creep cavities, can also play a key role in Type IV fracture of welded joint in 9% Cr steels.

LanguageEnglish
Pages60-69
Number of pages10
JournalJournal of Materials Processing Technology
Volume219
DOIs
Publication statusPublished - 2015

Fingerprint

Heat Affected Zone
Tungsten
Steel
Heat affected zone
Aging of materials
Grain Boundary
Coarsening
Metals
Welds
Grain boundaries
Precipitates
Welded Joints
Thermal aging
Creep
Austenite
Age hardening
Heat Treatment
Tempering
Hardening
Dislocation

Cite this

@article{2fec6058495242da9abd28bdf978aed8,
title = "Laves-phase evolution during aging in fine grained heat-affected zone of a tungsten-strengthened 9{\%} Cr steel weldment",
abstract = "The precipitation and coarsening of Laves-phase in the fine grained heat-affected zone (FGHAZ) of a 9{\%} Cr steel P92 welded joint during thermal aging at 923 K were investigated and compared to the base metal (BM), in order to clarify their effects on the Type IV fracture. Laves-phase precipitated mostly on the prior austenite grain boundaries of the FGHAZ. In comparison with BM, FGHAZ contained more grain boundary areas and can provide more nucleation sites for Laves-phase, resulting in an accelerated precipitation and rapidly reaching to the around 1.0{\%} of saturated volume fraction. The coarsening of Laves-phase precipitates in FGHAZ was also much faster than that in BM, enhanced by the contribution of grain boundary diffusion resulted from its finer prior austenite grains. The FGHAZ had denser and smaller Laves-phase precipitates during the precipitation period in comparison with BM, obviously improved the creep strength by precipitation hardening. However, this effect in FGHAZ reduced sharply during coarsening owing to its coarsening rate greater than that of BM. In addition to the initial coarse polygonal subgrains with low dislocation density in FGHAZ produced by the weld thermal cycle and subsequent tempering in post-weld heat treatment (PWHT), coarse Laves-phase precipitates on grain boundaries formed in the long-term thermal aging, contributing to the formation of the creep cavities, can also play a key role in Type IV fracture of welded joint in 9{\%} Cr steels.",
keywords = "Alloys Welding, Electron microscopy, Microstructure, Precipitation and coarsening",
author = "Xue Wang and Qiang Xu and Yu, {Shu Min} and Hong Liu and Lei Hu and Ren, {Yao Yao}",
year = "2015",
doi = "10.1016/j.jmatprotec.2014.12.007",
language = "English",
volume = "219",
pages = "60--69",
journal = "Journal of Materials Processing Technology",
issn = "0924-0136",
publisher = "Elsevier BV",

}

Laves-phase evolution during aging in fine grained heat-affected zone of a tungsten-strengthened 9% Cr steel weldment. / Wang, Xue; Xu, Qiang; Yu, Shu Min; Liu, Hong; Hu, Lei; Ren, Yao Yao.

In: Journal of Materials Processing Technology, Vol. 219, 2015, p. 60-69.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Laves-phase evolution during aging in fine grained heat-affected zone of a tungsten-strengthened 9% Cr steel weldment

AU - Wang, Xue

AU - Xu, Qiang

AU - Yu, Shu Min

AU - Liu, Hong

AU - Hu, Lei

AU - Ren, Yao Yao

PY - 2015

Y1 - 2015

N2 - The precipitation and coarsening of Laves-phase in the fine grained heat-affected zone (FGHAZ) of a 9% Cr steel P92 welded joint during thermal aging at 923 K were investigated and compared to the base metal (BM), in order to clarify their effects on the Type IV fracture. Laves-phase precipitated mostly on the prior austenite grain boundaries of the FGHAZ. In comparison with BM, FGHAZ contained more grain boundary areas and can provide more nucleation sites for Laves-phase, resulting in an accelerated precipitation and rapidly reaching to the around 1.0% of saturated volume fraction. The coarsening of Laves-phase precipitates in FGHAZ was also much faster than that in BM, enhanced by the contribution of grain boundary diffusion resulted from its finer prior austenite grains. The FGHAZ had denser and smaller Laves-phase precipitates during the precipitation period in comparison with BM, obviously improved the creep strength by precipitation hardening. However, this effect in FGHAZ reduced sharply during coarsening owing to its coarsening rate greater than that of BM. In addition to the initial coarse polygonal subgrains with low dislocation density in FGHAZ produced by the weld thermal cycle and subsequent tempering in post-weld heat treatment (PWHT), coarse Laves-phase precipitates on grain boundaries formed in the long-term thermal aging, contributing to the formation of the creep cavities, can also play a key role in Type IV fracture of welded joint in 9% Cr steels.

AB - The precipitation and coarsening of Laves-phase in the fine grained heat-affected zone (FGHAZ) of a 9% Cr steel P92 welded joint during thermal aging at 923 K were investigated and compared to the base metal (BM), in order to clarify their effects on the Type IV fracture. Laves-phase precipitated mostly on the prior austenite grain boundaries of the FGHAZ. In comparison with BM, FGHAZ contained more grain boundary areas and can provide more nucleation sites for Laves-phase, resulting in an accelerated precipitation and rapidly reaching to the around 1.0% of saturated volume fraction. The coarsening of Laves-phase precipitates in FGHAZ was also much faster than that in BM, enhanced by the contribution of grain boundary diffusion resulted from its finer prior austenite grains. The FGHAZ had denser and smaller Laves-phase precipitates during the precipitation period in comparison with BM, obviously improved the creep strength by precipitation hardening. However, this effect in FGHAZ reduced sharply during coarsening owing to its coarsening rate greater than that of BM. In addition to the initial coarse polygonal subgrains with low dislocation density in FGHAZ produced by the weld thermal cycle and subsequent tempering in post-weld heat treatment (PWHT), coarse Laves-phase precipitates on grain boundaries formed in the long-term thermal aging, contributing to the formation of the creep cavities, can also play a key role in Type IV fracture of welded joint in 9% Cr steels.

KW - Alloys Welding

KW - Electron microscopy

KW - Microstructure

KW - Precipitation and coarsening

UR - http://www.scopus.com/inward/record.url?scp=84919928443&partnerID=8YFLogxK

U2 - 10.1016/j.jmatprotec.2014.12.007

DO - 10.1016/j.jmatprotec.2014.12.007

M3 - Article

VL - 219

SP - 60

EP - 69

JO - Journal of Materials Processing Technology

T2 - Journal of Materials Processing Technology

JF - Journal of Materials Processing Technology

SN - 0924-0136

ER -