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Title: Effect of Pre-Weld Heat Treatment on Microstructure and Creep Strength of ICHAZ in Grade 91 Steel

Abstract

In this work, Grade 91 base metal was normalized with two different cooling conditions, water quenching and air cooling. The intercritical welding thermal cycle simulated by using the Gleeble system were applied to the heat-treated base metals to reproduce the intercritical heat-affected zone (ICHAZ). Microstructure, including precipitate and tempered martensite, of the base metal and ICHAZ was carefully characterized with advanced microscopy techniques. Creep strength of the simulated ICHAZs was evaluated at a high creep temperature of 650 °C with a stress of 100 MPa. A correlation between the microstructure and creep behavior of the ICHAZ is built to understand creep rupture mechanisms in the ICHAZ. The results show that more coarse carbides precipitated along the prior austenite grain boundaries after tempering in the water-quenched base metal. These carbides cannot be fully dissolved by the intercritical welding thermal cycle. The simulated ICHAZ generated from the water-quenched base metal underwent a higher grain recovery and growth during the typical post-weld heat treatment at 760 °C. Both simulated ICHAZs from two pre-weld heat treated base metals exhibit an extremely low creep resistance with a typical ductile fracture during creep testing. The faster grain growth and precipitate coarsening in the ICHAZ, simulated frommore » the water-quenched base metal, made it even worse.« less

Authors:
ORCiD logo [1];  [1]; ORCiD logo [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Fossil Energy (FE)
OSTI Identifier:
1545216
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: ASME Pressure Vessels & Piping Conference (PVP 2019) - San Antonio, Texas, United States of America - 7/14/2019 8:00:00 AM-7/19/2019 8:00:00 AM
Country of Publication:
United States
Language:
English

Citation Formats

Wang, Yiyu, Zhang, Wei, and Feng, Zhili. Effect of Pre-Weld Heat Treatment on Microstructure and Creep Strength of ICHAZ in Grade 91 Steel. United States: N. p., 2019. Web.
Wang, Yiyu, Zhang, Wei, & Feng, Zhili. Effect of Pre-Weld Heat Treatment on Microstructure and Creep Strength of ICHAZ in Grade 91 Steel. United States.
Wang, Yiyu, Zhang, Wei, and Feng, Zhili. Mon . "Effect of Pre-Weld Heat Treatment on Microstructure and Creep Strength of ICHAZ in Grade 91 Steel". United States. https://www.osti.gov/servlets/purl/1545216.
@article{osti_1545216,
title = {Effect of Pre-Weld Heat Treatment on Microstructure and Creep Strength of ICHAZ in Grade 91 Steel},
author = {Wang, Yiyu and Zhang, Wei and Feng, Zhili},
abstractNote = {In this work, Grade 91 base metal was normalized with two different cooling conditions, water quenching and air cooling. The intercritical welding thermal cycle simulated by using the Gleeble system were applied to the heat-treated base metals to reproduce the intercritical heat-affected zone (ICHAZ). Microstructure, including precipitate and tempered martensite, of the base metal and ICHAZ was carefully characterized with advanced microscopy techniques. Creep strength of the simulated ICHAZs was evaluated at a high creep temperature of 650 °C with a stress of 100 MPa. A correlation between the microstructure and creep behavior of the ICHAZ is built to understand creep rupture mechanisms in the ICHAZ. The results show that more coarse carbides precipitated along the prior austenite grain boundaries after tempering in the water-quenched base metal. These carbides cannot be fully dissolved by the intercritical welding thermal cycle. The simulated ICHAZ generated from the water-quenched base metal underwent a higher grain recovery and growth during the typical post-weld heat treatment at 760 °C. Both simulated ICHAZs from two pre-weld heat treated base metals exhibit an extremely low creep resistance with a typical ductile fracture during creep testing. The faster grain growth and precipitate coarsening in the ICHAZ, simulated from the water-quenched base metal, made it even worse.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {7}
}

Conference:
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