Effect of a heat treatment on the precipitation behavior and tensile properties of alloy 690 steam generator tubes

Abstract

The intergranular carbide precipitation behavior and its effect on the tensile properties were investigated in alloy 690. The precipitation of intergranular carbides, identified as Cr-rich M23C6, was retarded on the low-angle grain boundaries and the coincidence-site lattice boundaries. The M23C6 carbides have a cube-cube orientation relationship with the matrix. The ultimate tensile strength, yield strength, and elongation of the solution annealed alloy 690 are 648.2 ± 8.2 MPa, 242.8 ± 10.5 MPa and 44.9 ± 2.3%, respectively. The ultimate tensile strength and the yield strength increased to 764.8 ± 7.8 MPa and 364.8 ± 10.2 MPa until the aging time reached 16 h. This increase is ascribed to the M23C6 carbide acting as reinforcements. However, when the aging time exceed 16 h, these properties gradually decreased with increasing aging time. The decrease in ultimate tensile strength, yield strength, and elongation were mainly caused by the intergranular cracking due to the low bond strength between the carbide and the matrix.

Metadata

Item Type:	Article
Authors/Creators:	Lee, T-H. Suh, H-Y. Han, S-K. Noh, J-S. Lee, J-H. (http://orcid.org/0000-0003-3193-9128)
Copyright, Publisher and Additional Information:	© 2016 Elsevier. This is an author produced version of a paper subsequently published in Journal of Nuclear Materials. Uploaded in accordance with the publisher's self-archiving policy. Article available under the terms of the CC-BY-NC-ND licence (https://creativecommons.org/licenses/by-nc-nd/4.0/)
Keywords:	Alloy 690; Heat treatment; M23C6 carbide; Grain boundary character; Tensile properties
Dates:	Published: 24 June 2016 Published: October 2016 Published (online): 22 June 2016 Accepted: 22 June 2016
Institution:	The University of Sheffield
Academic Units:	The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Materials Science and Engineering (Sheffield)
Depositing User:	Symplectic Sheffield
Date Deposited:	21 Jul 2016 08:57
Last Modified:	06 Nov 2017 10:02
Published Version:	https://dx.doi.org/10.1016/j.jnucmat.2016.06.038
Status:	Published
Publisher:	Elsevier
Refereed:	Yes
Identification Number:	10.1016/j.jnucmat.2016.06.038
Open Archives Initiative ID (OAI ID):	oai:eprints.whiterose.ac.uk:102510