Basic Microstructural Characterization of Second Phases in Homogeneous Weld Joint Made of X6CrNiNbN25-20 Steel After Long-Term Exposure Time at 973 K
Identifikátory výsledku
Kód výsledku v IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F26722445%3A_____%2F21%3AN0000013" target="_blank" >RIV/26722445:_____/21:N0000013 - isvavai.cz</a>
Výsledek na webu
<a href="https://asmedigitalcollection.asme.org/nuclearengineering/article-abstract/7/2/024505/1089047/Basic-Microstructural-Characterization-of-Second?redirectedFrom=fulltext" target="_blank" >https://asmedigitalcollection.asme.org/nuclearengineering/article-abstract/7/2/024505/1089047/Basic-Microstructural-Characterization-of-Second?redirectedFrom=fulltext</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1115/1.4048900" target="_blank" >10.1115/1.4048900</a>
Alternativní jazyky
Jazyk výsledku
angličtina
Název v původním jazyce
Basic Microstructural Characterization of Second Phases in Homogeneous Weld Joint Made of X6CrNiNbN25-20 Steel After Long-Term Exposure Time at 973 K
Popis výsledku v původním jazyce
New blocks of fossil fuel power plants designed for steam temperatures above 873 K require advanced stainless steels as material for superheater or reheater systems. Weld joints are critical parts in fossil power units. Great attention is paid to the exploitation of new steel grades with higher material properties. In the austenitic steels family, the superior grade is undoubtedly HR3C steel (X6CrNiNbN25-20). A detailed knowledge on stability and microstructure composition during thermal exposure of the weld joints made from HR3C is necessary in order to use them in fossil fuel power plants with ultrasupercritical (USC) and new advanced ultrasupercritical (A-USC) steam parameters. The aim of the paper is to identify critical minor phases in HR3C steel, which allow acceleration of creep damage. The sigma-phase and rough carbides M23C6 type is considered as such a phases in this steel. In this study, the sigma-phase is identified and studied in more detail in relation to the development of creep damage at 973 K. Experimental material of the homogeneous HR3C weld joints in two states: in the as-welded state (AW) and after the postweld heat treatment (PWHT). Weld joints were manufactured by orbital welding using the gas tungsten arc welding (GTAW) method, heat input Q(s) = 1600 J/mm, interpass 423 K, three beads. Nickel-base alloy UTP A6170 Co (equivalent to Thermanit 617) was used as a filler material. The PWHT was carried out at the temperature of 1503 K for 15 min. Stress rupture tests were performed on the cross-weld (CW) joints of tubes o 38 x 6.3 mm at 973 K with times to rupture up to nearly 22,000 h. The polished surface of the longitudinal sections was subjected to color etching in Murakami (30 g K-3(Fe(CN)(6)), 30 g KOH, 60 ml H2O) in order to highlight the sigma-phase. Several microscopic techniques were used for the study. The results were supplemented by creep, grain size, and microhardness data hardness vickers (HV) 0.5. The PWHT specimens exhibited an average sigma-phase size of approximately 5 mu m as well as AW specimens in specimens with short time to rupture (t(r)). However, t(r) such as 20,000 h, the average sigma-phase size already reached dangerous border 10 mu m. The AW specimens as opposed to the PWHT specimens did not show a noticeable growth of austenitic grains in the heat-affected zone (HAZ). In specimens after PWHT, the average grain size in HAZ was more than twice that of the body material (BM). It is worth noting that creep ductility values of specimens in the state after PWHT are very low, which is the result of coarse-grained structure in the HAZ and accelerated precipitation of sigma-phase particles along grain boundaries during creep at 973 K.
Název v anglickém jazyce
Basic Microstructural Characterization of Second Phases in Homogeneous Weld Joint Made of X6CrNiNbN25-20 Steel After Long-Term Exposure Time at 973 K
Popis výsledku anglicky
New blocks of fossil fuel power plants designed for steam temperatures above 873 K require advanced stainless steels as material for superheater or reheater systems. Weld joints are critical parts in fossil power units. Great attention is paid to the exploitation of new steel grades with higher material properties. In the austenitic steels family, the superior grade is undoubtedly HR3C steel (X6CrNiNbN25-20). A detailed knowledge on stability and microstructure composition during thermal exposure of the weld joints made from HR3C is necessary in order to use them in fossil fuel power plants with ultrasupercritical (USC) and new advanced ultrasupercritical (A-USC) steam parameters. The aim of the paper is to identify critical minor phases in HR3C steel, which allow acceleration of creep damage. The sigma-phase and rough carbides M23C6 type is considered as such a phases in this steel. In this study, the sigma-phase is identified and studied in more detail in relation to the development of creep damage at 973 K. Experimental material of the homogeneous HR3C weld joints in two states: in the as-welded state (AW) and after the postweld heat treatment (PWHT). Weld joints were manufactured by orbital welding using the gas tungsten arc welding (GTAW) method, heat input Q(s) = 1600 J/mm, interpass 423 K, three beads. Nickel-base alloy UTP A6170 Co (equivalent to Thermanit 617) was used as a filler material. The PWHT was carried out at the temperature of 1503 K for 15 min. Stress rupture tests were performed on the cross-weld (CW) joints of tubes o 38 x 6.3 mm at 973 K with times to rupture up to nearly 22,000 h. The polished surface of the longitudinal sections was subjected to color etching in Murakami (30 g K-3(Fe(CN)(6)), 30 g KOH, 60 ml H2O) in order to highlight the sigma-phase. Several microscopic techniques were used for the study. The results were supplemented by creep, grain size, and microhardness data hardness vickers (HV) 0.5. The PWHT specimens exhibited an average sigma-phase size of approximately 5 mu m as well as AW specimens in specimens with short time to rupture (t(r)). However, t(r) such as 20,000 h, the average sigma-phase size already reached dangerous border 10 mu m. The AW specimens as opposed to the PWHT specimens did not show a noticeable growth of austenitic grains in the heat-affected zone (HAZ). In specimens after PWHT, the average grain size in HAZ was more than twice that of the body material (BM). It is worth noting that creep ductility values of specimens in the state after PWHT are very low, which is the result of coarse-grained structure in the HAZ and accelerated precipitation of sigma-phase particles along grain boundaries during creep at 973 K.
Klasifikace
Druh
J<sub>imp</sub> - Článek v periodiku v databázi Web of Science
CEP obor
—
OECD FORD obor
20305 - Nuclear related engineering; (nuclear physics to be 1.3);
Návaznosti výsledku
Projekt
<a href="/cs/project/LQ1603" target="_blank" >LQ1603: Výzkum pro SUSEN</a><br>
Návaznosti
P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)
Ostatní
Rok uplatnění
2021
Kód důvěrnosti údajů
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Údaje specifické pro druh výsledku
Název periodika
Journal of Nuclear Engineering and Radiation Science
ISSN
2332-8983
e-ISSN
2332-8975
Svazek periodika
7
Číslo periodika v rámci svazku
2
Stát vydavatele periodika
NL - Nizozemsko
Počet stran výsledku
5
Strana od-do
1-5
Kód UT WoS článku
000630005800012
EID výsledku v databázi Scopus
2-s2.0-85097461096