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Title: An Investigation of Creep Resistance in Grade 91 Steel through Computational Thermodynamics

Abstract

This study was conducted to understand the relationship between various critical temperatures and the stability of the secondary phases inside the heat-affected-zone (HAZ) of welded Grade 91 (Gr.91) steel parts. Type IV cracking has been observed in the HAZ, and it is widely accepted that the stabilities of the secondary phases in Gr.91 steel are critical to the creep resistance, which is related to the crack failure of this steel. In this work, the stabilities of the secondary phases, including those of the M23C6, MX, and Z phases, were simulated by computational thermodynamics. Equilibrium cooling and Scheil simulations were carried out in order to understand the phase stability in welded Gr.91 steel. The effect of four critical temperatures—that is, Ac1 (the threshold temperature at which austenite begins to form), Ac3 (the threshold temperature at which ferrite is fully transformed into austenite), and the M23C6 and Z phase threshold temperatures—on the thickness of the HAZ and phase stability in the HAZ is discussed. Overall, the simulations presented in this paper explain the mechanisms that can affect the creep resistance of Gr.91 steel, and can offer a possible solution to the problem of how to increase creep resistance at elevated temperatures bymore » optimizing the steel composition, welding, and heat treatment process parameters. The simulation results from this work provide guidance for future alloy development to improve creep resistance in order to prevent type IV cracking.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Florida International Univ., Miami, FL (United States)
Sponsoring Org.:
USDOE Office of Fossil Energy (FE)
Contributing Org.:
Worcester Polytechnic Institute
OSTI Identifier:
1595169
Alternate Identifier(s):
OSTI ID: 1599749; OSTI ID: 1669887
Grant/Contract Number:  
FE0027800
Resource Type:
Published Article
Journal Name:
Engineering
Additional Journal Information:
Journal Name: Engineering Journal Volume: 6 Journal Issue: 6; Journal ID: ISSN 2095-8099
Publisher:
Engineering Sciences Press
Country of Publication:
China
Language:
English
Subject:
36 MATERIALS SCIENCE; Grade 91 steel; Creep resistance; Ferritic-martensitic steels; Welding microstructure; Computational thermodynamics; Secondary phase; Alloy composition; Grade 91 steelCreep resistanceFerritic–martensitic steelsWelding microstructureComputational thermodynamicsSecondary phaseAlloy composition

Citation Formats

Smith, Andrew, Asadikiya, Mohammad, Yang, Mei, Chen, Jiuhua, and Zhong, Yu. An Investigation of Creep Resistance in Grade 91 Steel through Computational Thermodynamics. China: N. p., 2019. Web. doi:10.1016/j.eng.2019.12.004.
Smith, Andrew, Asadikiya, Mohammad, Yang, Mei, Chen, Jiuhua, & Zhong, Yu. An Investigation of Creep Resistance in Grade 91 Steel through Computational Thermodynamics. China. https://doi.org/10.1016/j.eng.2019.12.004
Smith, Andrew, Asadikiya, Mohammad, Yang, Mei, Chen, Jiuhua, and Zhong, Yu. Sun . "An Investigation of Creep Resistance in Grade 91 Steel through Computational Thermodynamics". China. https://doi.org/10.1016/j.eng.2019.12.004.
@article{osti_1595169,
title = {An Investigation of Creep Resistance in Grade 91 Steel through Computational Thermodynamics},
author = {Smith, Andrew and Asadikiya, Mohammad and Yang, Mei and Chen, Jiuhua and Zhong, Yu},
abstractNote = {This study was conducted to understand the relationship between various critical temperatures and the stability of the secondary phases inside the heat-affected-zone (HAZ) of welded Grade 91 (Gr.91) steel parts. Type IV cracking has been observed in the HAZ, and it is widely accepted that the stabilities of the secondary phases in Gr.91 steel are critical to the creep resistance, which is related to the crack failure of this steel. In this work, the stabilities of the secondary phases, including those of the M23C6, MX, and Z phases, were simulated by computational thermodynamics. Equilibrium cooling and Scheil simulations were carried out in order to understand the phase stability in welded Gr.91 steel. The effect of four critical temperatures—that is, Ac1 (the threshold temperature at which austenite begins to form), Ac3 (the threshold temperature at which ferrite is fully transformed into austenite), and the M23C6 and Z phase threshold temperatures—on the thickness of the HAZ and phase stability in the HAZ is discussed. Overall, the simulations presented in this paper explain the mechanisms that can affect the creep resistance of Gr.91 steel, and can offer a possible solution to the problem of how to increase creep resistance at elevated temperatures by optimizing the steel composition, welding, and heat treatment process parameters. The simulation results from this work provide guidance for future alloy development to improve creep resistance in order to prevent type IV cracking.},
doi = {10.1016/j.eng.2019.12.004},
journal = {Engineering},
number = 6,
volume = 6,
place = {China},
year = {2019},
month = {12}
}

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