Optimization of PWHT of Simulated HAZ Subzones in P91 Steel with Respect to Hardness and Impact Toughness

Appropriate post weld heat treatment (PWHT) is usually obligatory when creep resistant steels are welded for thermal power plant components that operate at elevated temperatures for 30-40 years. The influence of different PWHTs on the microstructure, hardness, and impact toughness of simulated heat...

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Main Authors: Gorazd Lojen, Tomaž Vuherer
Format: Article
Language:English
Published: MDPI AG 2020-09-01
Series:Metals
Subjects:
Online Access:https://www.mdpi.com/2075-4701/10/9/1215
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spelling doaj-0db5d374ceb742a8a21a025ee7537f942020-11-25T02:30:43ZengMDPI AGMetals2075-47012020-09-01101215121510.3390/met10091215Optimization of PWHT of Simulated HAZ Subzones in P91 Steel with Respect to Hardness and Impact ToughnessGorazd Lojen0Tomaž Vuherer1Faculty of mechanical engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, SloveniaFaculty of mechanical engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, SloveniaAppropriate post weld heat treatment (PWHT) is usually obligatory when creep resistant steels are welded for thermal power plant components that operate at elevated temperatures for 30-40 years. The influence of different PWHTs on the microstructure, hardness, and impact toughness of simulated heat affected zone (HAZ) subzones was studied. Thereby, coarse grained HAZ, two different fine grained HAZ areas, and intercritical HAZ were subjected to 20 different PWHTs at temperatures 740–800 °C and durations 0.5–8 h. It was found that the most commonly recommended PWHT, of 3 h or less at 760 °C, is insufficient with respect to the hardness and impact toughness of coarse grained HAZ. To obtain a Vickers hardness ≤ 265 <i>HV</i> and impact toughness at least equal to the impact toughness of the base metal (192 J) in the coarse grained HAZ, it took 8 h at 740 °C, 4 h at 760 °C, more than 1 h at 780 °C, and 0.5 h and 800 °C. Even after 8 h at 800 °C, mechanical properties were still within the target range. The most recommendable post weld heat treatments at 780 °C for 1.2–2 h or at 760 °C for 3–4 h were identified. All specimens subjected to these treatments exhibited appropriate hardness, impact toughness, and microstructure.https://www.mdpi.com/2075-4701/10/9/1215post weld heat treatmentHAZ subzone simulationimpact toughnesscrack initiation energycrack propagation energy.
collection DOAJ
language English
format Article
sources DOAJ
author Gorazd Lojen
Tomaž Vuherer
spellingShingle Gorazd Lojen
Tomaž Vuherer
Optimization of PWHT of Simulated HAZ Subzones in P91 Steel with Respect to Hardness and Impact Toughness
Metals
post weld heat treatment
HAZ subzone simulation
impact toughness
crack initiation energy
crack propagation energy.
author_facet Gorazd Lojen
Tomaž Vuherer
author_sort Gorazd Lojen
title Optimization of PWHT of Simulated HAZ Subzones in P91 Steel with Respect to Hardness and Impact Toughness
title_short Optimization of PWHT of Simulated HAZ Subzones in P91 Steel with Respect to Hardness and Impact Toughness
title_full Optimization of PWHT of Simulated HAZ Subzones in P91 Steel with Respect to Hardness and Impact Toughness
title_fullStr Optimization of PWHT of Simulated HAZ Subzones in P91 Steel with Respect to Hardness and Impact Toughness
title_full_unstemmed Optimization of PWHT of Simulated HAZ Subzones in P91 Steel with Respect to Hardness and Impact Toughness
title_sort optimization of pwht of simulated haz subzones in p91 steel with respect to hardness and impact toughness
publisher MDPI AG
series Metals
issn 2075-4701
publishDate 2020-09-01
description Appropriate post weld heat treatment (PWHT) is usually obligatory when creep resistant steels are welded for thermal power plant components that operate at elevated temperatures for 30-40 years. The influence of different PWHTs on the microstructure, hardness, and impact toughness of simulated heat affected zone (HAZ) subzones was studied. Thereby, coarse grained HAZ, two different fine grained HAZ areas, and intercritical HAZ were subjected to 20 different PWHTs at temperatures 740–800 °C and durations 0.5–8 h. It was found that the most commonly recommended PWHT, of 3 h or less at 760 °C, is insufficient with respect to the hardness and impact toughness of coarse grained HAZ. To obtain a Vickers hardness ≤ 265 <i>HV</i> and impact toughness at least equal to the impact toughness of the base metal (192 J) in the coarse grained HAZ, it took 8 h at 740 °C, 4 h at 760 °C, more than 1 h at 780 °C, and 0.5 h and 800 °C. Even after 8 h at 800 °C, mechanical properties were still within the target range. The most recommendable post weld heat treatments at 780 °C for 1.2–2 h or at 760 °C for 3–4 h were identified. All specimens subjected to these treatments exhibited appropriate hardness, impact toughness, and microstructure.
topic post weld heat treatment
HAZ subzone simulation
impact toughness
crack initiation energy
crack propagation energy.
url https://www.mdpi.com/2075-4701/10/9/1215
work_keys_str_mv AT gorazdlojen optimizationofpwhtofsimulatedhazsubzonesinp91steelwithrespecttohardnessandimpacttoughness
AT tomazvuherer optimizationofpwhtofsimulatedhazsubzonesinp91steelwithrespecttohardnessandimpacttoughness
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