Correlation of precipitate stability to increased creep resistance of Cr-Mo steel welds

X. Yu; S. S. Babu; H. Terasaki; Y. Komizo; Y. Yamamoto; M. L. Santella

doi:10.1016/j.actamat.2012.12.040

Correlation of precipitate stability to increased creep resistance of Cr-Mo steel welds

X. Yu, S. S. Babu, H. Terasaki, Y. Komizo, Y. Yamamoto, M. L. Santella

Alloy Behavior & Design

Research output: Contribution to journal › Article › peer-review

62 Scopus citations

Abstract

An order of magnitude decrease (from 16.0 × 10^-4 to 4.1 × 10^-4% h^-1) in steady-state creep rate was observed in the fine-grained heat-affected zone (HAZ) of a Cr-Mo steel weld by the reduction of the pre-weld tempering temperature from 760 °C (HTT) to 650 °C (LTT). The microstructure during each stage of the manufacturing path, including pre-weld temper, thermal cycling and post-weld heat treatment, was characterized using a suite of characterization techniques. The techniques included simulated thermal cycling, dilatometry and electron microscopy, as well as time-resolved X-ray diffraction using Synchrotron radiation. Both LTT and HTT steels before welding contain M₂₃C₆ (M = Cr, Fe) and MX (M = Nb, V; X = C, N) precipitates in a tempered martensite matrix. During simulated HAZ thermal cycling with different peak temperatures, changes in M₂₃C₆ carbide characteristics were observed between the HTT and LLT conditions, while MX precipitates remained stable in both conditions. Simulated post-weld heat treatment samples show larger M ₂₃C₆ in the HTT condition than in the LTT condition. The results provide a solution to extending the life of Cr-Mo steel welded structures used in power plants.

Original language	English
Pages (from-to)	2194-2206
Number of pages	13
Journal	Acta Materialia
Volume	61
Issue number	6
DOIs	https://doi.org/10.1016/j.actamat.2012.12.040
State	Published - Apr 2013

Funding

The authors greatly thank Thomas Muth and Dr. Lizhen Tan for technically reviewing this manuscript. This research was conducted as part of the Fossil Energy Advanced Research Materials Program, which is sponsored by Office of Fossil Energy, U.S. Department of Energy, National Energy Technology Laboratory. The synchrotron radiation experiments were performed at the BL46XU of SPring-8 as the Priority Research Proposal (priority filed: Industrial Application) with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (Proposal No. 2011B1968).

Funders	Funder number
U.S. Department of Energy
Office of Fossil Energy
National Energy Technology Laboratory
Japan Society for the Promotion of Science	23246127

Keywords

Cr-Mo steels
Heat-affected zone
P91 grade
Tempering
Welding

Access to Document

10.1016/j.actamat.2012.12.040

Cite this

@article{839872dd0e954a9abd4d6751cee3bfaf,

title = "Correlation of precipitate stability to increased creep resistance of Cr-Mo steel welds",

abstract = "An order of magnitude decrease (from 16.0 × 10-4 to 4.1 × 10-4% h-1) in steady-state creep rate was observed in the fine-grained heat-affected zone (HAZ) of a Cr-Mo steel weld by the reduction of the pre-weld tempering temperature from 760 °C (HTT) to 650 °C (LTT). The microstructure during each stage of the manufacturing path, including pre-weld temper, thermal cycling and post-weld heat treatment, was characterized using a suite of characterization techniques. The techniques included simulated thermal cycling, dilatometry and electron microscopy, as well as time-resolved X-ray diffraction using Synchrotron radiation. Both LTT and HTT steels before welding contain M23C6 (M = Cr, Fe) and MX (M = Nb, V; X = C, N) precipitates in a tempered martensite matrix. During simulated HAZ thermal cycling with different peak temperatures, changes in M23C6 carbide characteristics were observed between the HTT and LLT conditions, while MX precipitates remained stable in both conditions. Simulated post-weld heat treatment samples show larger M 23C6 in the HTT condition than in the LTT condition. The results provide a solution to extending the life of Cr-Mo steel welded structures used in power plants.",

keywords = "Cr-Mo steels, Heat-affected zone, P91 grade, Tempering, Welding",

author = "X. Yu and Babu, {S. S.} and H. Terasaki and Y. Komizo and Y. Yamamoto and Santella, {M. L.}",

year = "2013",

month = apr,

doi = "10.1016/j.actamat.2012.12.040",

language = "English",

volume = "61",

pages = "2194--2206",

journal = "Acta Materialia",

issn = "1359-6454",

publisher = "Elsevier",

number = "6",

}

TY - JOUR

T1 - Correlation of precipitate stability to increased creep resistance of Cr-Mo steel welds

AU - Yu, X.

AU - Babu, S. S.

AU - Terasaki, H.

AU - Komizo, Y.

AU - Yamamoto, Y.

AU - Santella, M. L.

PY - 2013/4

Y1 - 2013/4

N2 - An order of magnitude decrease (from 16.0 × 10-4 to 4.1 × 10-4% h-1) in steady-state creep rate was observed in the fine-grained heat-affected zone (HAZ) of a Cr-Mo steel weld by the reduction of the pre-weld tempering temperature from 760 °C (HTT) to 650 °C (LTT). The microstructure during each stage of the manufacturing path, including pre-weld temper, thermal cycling and post-weld heat treatment, was characterized using a suite of characterization techniques. The techniques included simulated thermal cycling, dilatometry and electron microscopy, as well as time-resolved X-ray diffraction using Synchrotron radiation. Both LTT and HTT steels before welding contain M23C6 (M = Cr, Fe) and MX (M = Nb, V; X = C, N) precipitates in a tempered martensite matrix. During simulated HAZ thermal cycling with different peak temperatures, changes in M23C6 carbide characteristics were observed between the HTT and LLT conditions, while MX precipitates remained stable in both conditions. Simulated post-weld heat treatment samples show larger M 23C6 in the HTT condition than in the LTT condition. The results provide a solution to extending the life of Cr-Mo steel welded structures used in power plants.

AB - An order of magnitude decrease (from 16.0 × 10-4 to 4.1 × 10-4% h-1) in steady-state creep rate was observed in the fine-grained heat-affected zone (HAZ) of a Cr-Mo steel weld by the reduction of the pre-weld tempering temperature from 760 °C (HTT) to 650 °C (LTT). The microstructure during each stage of the manufacturing path, including pre-weld temper, thermal cycling and post-weld heat treatment, was characterized using a suite of characterization techniques. The techniques included simulated thermal cycling, dilatometry and electron microscopy, as well as time-resolved X-ray diffraction using Synchrotron radiation. Both LTT and HTT steels before welding contain M23C6 (M = Cr, Fe) and MX (M = Nb, V; X = C, N) precipitates in a tempered martensite matrix. During simulated HAZ thermal cycling with different peak temperatures, changes in M23C6 carbide characteristics were observed between the HTT and LLT conditions, while MX precipitates remained stable in both conditions. Simulated post-weld heat treatment samples show larger M 23C6 in the HTT condition than in the LTT condition. The results provide a solution to extending the life of Cr-Mo steel welded structures used in power plants.

KW - Cr-Mo steels

KW - Heat-affected zone

KW - P91 grade

KW - Tempering

KW - Welding

UR - http://www.scopus.com/inward/record.url?scp=84874000916&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2012.12.040

DO - 10.1016/j.actamat.2012.12.040

M3 - Article

AN - SCOPUS:84874000916

SN - 1359-6454

VL - 61

SP - 2194

EP - 2206

JO - Acta Materialia

JF - Acta Materialia

IS - 6

ER -

Correlation of precipitate stability to increased creep resistance of Cr-Mo steel welds

Abstract

Funding

Keywords

Access to Document

Other files and links

Fingerprint

Cite this