Effect of Co Addition on the Creep Rupture Properties of 9Cr-1.8W-xCo Weld Metals

Fikret Kabakcı, Mustafa Acarer*, Murat Baydoğan, A. Selçuk Keskinkılıç, Filiz K. Acar, Hüseyin Çimenoğlu

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6 Atıf (Scopus)

Özet

In this study, the effect of Co addition on the microstructure and creep rupture properties of 9Cr-1.8W-xCo weld metals is investigated. Herein, stick electrodes were fabricated for producing weld metals with 0.5, 1.0, and 1.5 wt pct Co and without Co, which were then processed by post-welding heat treatment at 760 °C for 4 hours. The microstructures of weld metals, including the prior austenite grain size, tempered martensite lath size, delta ferrite content, and precipitate quantity and size, were characterized via optical microscopy, scanning and transmission electron microscopy, and electron backscattered diffraction. The precipitates were identified by X-ray diffraction after they were extracted from the matrix. The Curie temperature was determined via differential scanning calorimetry, which allowed the evaluation of diffusion rate as a function of Co content. The weld metals were mechanically characterized by creep rupture tests conducted at 675 °C under 150 MPa and by hardness and tensile tests conducted at room temperature as well as Charpy impact tests conducted at various temperatures from − 40 °C to 60 °C. The results obtained herein suggest that the addition of Co significantly increases the creep rupture time of 9Cr-1.8W steel (by approximately 20 times than that of Co-free steel), reduces the prior austenite grain size and tempered martensite lath size, hinders the formation of detrimental delta ferrite, and promotes the formation of precipitates with slightly larger size. Herein, the highest creep resistance from the viewpoint of creep rupture time was obtained for 9Cr-1.8W weld metal with 1.5 wt pct Co. Furthermore, the results suggest that a finer and more stable substructure is required for improving the creep resistance.

Orijinal dilİngilizce
Sayfa (başlangıç-bitiş)129-142
Sayfa sayısı14
DergiMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Hacim52
Basın numarası1
DOI'lar
Yayın durumuYayınlandı - Oca 2021

Bibliyografik not

Publisher Copyright:
© 2020, The Minerals, Metals & Materials Society and ASM International.

Finansman

This study was carried out as a PhD thesis by FİKRET KABAKCI in the Graduate School of Natural and Applied Science at the Selçuk University, Konya, Turkey. The authors would like to acknowledge the financial support provided by SANTEZ (University-Industry Collaboration Grant Programme-Ministry of Science, Industry and Technology) with the Grant Number of 0374.STZ.2013-2. Authors also thank Gedik Welding Company, Istanbul, Turkey. This study was carried out as a PhD thesis by F?KRET KABAKCI in the Graduate School of Natural and Applied Science at the Sel?uk University, Konya, Turkey. The authors would like to acknowledge the financial support provided by SANTEZ (University-Industry Collaboration Grant Programme-Ministry of Science, Industry and Technology) with the Grant Number of 0374.STZ.2013-2. Authors also thank Gedik Welding Company, Istanbul, Turkey.

FinansörlerFinansör numarası
Gedik Welding Company
Graduate School of Natural and Applied Science
SANTEZ
University-Industry Collaboration Grant Programme-Ministry of Science, Industry and Technology0374.STZ.2013-2

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