Microstructural changes caused by yttrium addition to NbTi-modified centrifugally cast HP-type stainless steels

Journal Article · Thu Feb 15 04:00:00 EST 2007 · Materials Characterization

DOI:https://doi.org/10.1016/j.matchar.2006.04.007· OSTI ID:21003528

Nunes, F C ^[1]; Almeida, L.H. de ^[1]; Dille, J ^[2]; Delplancke, J -L ^[2]; Le May, I ^[3]

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1. Federal University of Rio de Janeiro (UFRJ), C.P. 68505, Ilha do Fundao, Rio de Janeiro (Brazil)
2. Free University of Brussels, C.P. 194/03, Av. F. D. Rooselvelt, 50, B-1050, Brussels (Belgium)
3. Metallurgical Consulting Services, P.O. Box 5006, Saskatoon, SK, S7K 4E3 (Canada)

Centrifugally cast heat-resistant HP stainless steels are particularly suitable for applications where service conditions comprise high temperatures and aggressive environments; thus, they are extensively used in reformer furnaces, in which hydrogen production takes place. The demand for better performance has motivated developments in these steels. The addition of Nb and Ti as microstructural modifiers has proved successful in providing a more stable microstructure. In this work yttrium was added to centrifugally cast NbTi-modified HP steels. It was observed that its presence increased the level of fragmentation of the chromium carbides, a positive aspect for creep resistance. The main cause of the fragmentation is the formation of yttrium carbides, which serve as heterogeneous nucleation sites for the other carbides. One of the tubes, with a lower titanium content, showed the best creep performance among those tubes studied owing to the presence of a smaller volume fraction of the deleterious G phase.

• OSTI ID: 21003528
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Journal Issue: 2 Vol. 58; ISSN 1044-5803; ISSN MACHEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CASTING
CASTINGS
CHROMIUM CARBIDES
CREEP
FRAGMENTATION
FURNACES
HEAT
HYDROGEN PRODUCTION
MICROSTRUCTURE
NUCLEATION
PERFORMANCE
STAINLESS STEELS
TITANIUM
YTTRIUM
YTTRIUM ADDITIONS
YTTRIUM CARBIDES