Straumal, B B and Kucheev, Y O and Efron, L I and Petelin, A L and Dutta Majumdar, Jyotsna and Manna, Indranil (2012) Complete and Incomplete Wetting of Ferrite Grain Boundaries by Austenite in the Low-Alloyed Ferritic Steel. Journal of Materials Engineering and Performance, 21 (5, SI). pp. 667-670. ISSN 1059-9495

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Abstract

Low-carbon low-alloyed ferritic steels are the main material for the production of high-strength pipes for the transportation of oil and gas. The formation of brittle carbide network during the lifetime of a pipeline could be a reason for a catastrophic failure. Among other reasons, it can be controlled by the morphology of grain boundary (GB) carbides. The microstructure of a low-alloyed ferritic steel containing 0.09 at.% C and small amounts of Si, Mn, Nb, Cu, Al, Ni, and Cr was studied between 300 and 900 A degrees C. The samples were annealed very long time (700 to 4000 h) in order to produce the equilibrium morphology of phases. The (alpha-Fe)/(alpha-Fe) GBs can be either completely or incompletely wetted (covered) by the gamma-Fe (austenite) above the temperature of eutectoid transition. The portion of (alpha-Fe)/(alpha-Fe) GBs completely wetted by gamma-Fe is around 90% and does not change much between 750 and 900 A degrees C. The (alpha-Fe)/(alpha-Fe) GBs can be either completely or incompletely wetted (covered) by the Fe3C (cementite) below the temperature of eutectoid transition. The portion of (alpha-Fe)/(alpha-Fe) GBs completely wetted by Fe3C changes below 680 A degrees C between 67 and 77%. The formation of the network of brittle cementite layers between ductile ferrite grains can explain the catastrophic failure of gas- and oil-pipelines after a certain lifetime.

Item Type: Article
Uncontrolled Keywords: Failure of pipelines; Ferritic steels; Grain boundaries; Low-alloyed steels; Wetting
Subjects: Engineering Materials
Divisions: Director´┐Żs Secretariat
Depositing User: Bidhan Chaudhuri
Date Deposited: 05 Jun 2012 10:10
Last Modified: 05 Jun 2012 10:10
URI: http://cgcri.csircentral.net/id/eprint/1482

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