Menu
Search
Filters
Close
Menu

51317--9717-Characterization of SCC Initiation Precursors in Cold-Worked Alloy 690

Picture for Characterization of SCC Initiation Precursors in Cold-Worked Alloy 690
Available for download

To evaluate the stress corrosion cracking initiation response of highly cold-worked UNS N06690, constant load tensile and blunt-notch compact tension testing were performed in 360°C simulated pressurized water reactor primary water.

Product Number: 51317--9717-SG
ISBN: 9717 2017 CP
Author: Karen Kruska
Publication Date: 2017
Industries: Materials Selection and Design , Science of Corrosion
$0.00
$20.00
$20.00

Due to its superior resistance to corrosion and stress corrosion cracking (SCC) high Cr Ni-base Alloy 690 is now commonly used in pressurized water reactors (PWRs). Even though highly cold-worked (CW) Alloy 690 has been shown to be susceptible to SCC crack growth in PWR primary water environments an open question remains whether SCC initiation was possible for these materials under constant load test conditions. Testing has been performed on a series of CW alloy 690 CRDM tubing specimens at constant load for up to 15000 hours in 360°C simulated PWR primary water. A companion paper will discuss the overall testing approach and describe results on different alloy 690 heats and cold work levels. The focus of the current paper is to illustrate the use of focused ion beam (FIB) scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for the high-resolution investigation of precursor damage and intergranular (IG) SCC crack nucleation in these specimens. Three-dimensional (3D) FIB/SEM imaging has been conducted on a series of IG precursors such as grain boundary (GB) oxides small cavities and even shallow cracks observed at the specimen surface. Contrast variations and EDS mapping were used to distinguish oxides carbides and cavities from the matrix material. Nanometer-sized cavities were observed associated with GB carbides in the highly CW specimens. Shallow IG cracks were present in the 30%CW specimens and exhibited oxidized crack flanks and a higher density of cavities ahead of the oxide front in all cases. The shape and distribution of carbides and cavities in the plain of the cracked GBs was analyzed in 3D to gain a mechanistic understanding of the processes that may be leading to SCC initiation in highly CW alloy 690.

Key words: 3D FIB/SEM, Ni-base alloys, SCC initiation, cold-work, UNS N6690, (Alloy 690)

Due to its superior resistance to corrosion and stress corrosion cracking (SCC) high Cr Ni-base Alloy 690 is now commonly used in pressurized water reactors (PWRs). Even though highly cold-worked (CW) Alloy 690 has been shown to be susceptible to SCC crack growth in PWR primary water environments an open question remains whether SCC initiation was possible for these materials under constant load test conditions. Testing has been performed on a series of CW alloy 690 CRDM tubing specimens at constant load for up to 15000 hours in 360°C simulated PWR primary water. A companion paper will discuss the overall testing approach and describe results on different alloy 690 heats and cold work levels. The focus of the current paper is to illustrate the use of focused ion beam (FIB) scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for the high-resolution investigation of precursor damage and intergranular (IG) SCC crack nucleation in these specimens. Three-dimensional (3D) FIB/SEM imaging has been conducted on a series of IG precursors such as grain boundary (GB) oxides small cavities and even shallow cracks observed at the specimen surface. Contrast variations and EDS mapping were used to distinguish oxides carbides and cavities from the matrix material. Nanometer-sized cavities were observed associated with GB carbides in the highly CW specimens. Shallow IG cracks were present in the 30%CW specimens and exhibited oxidized crack flanks and a higher density of cavities ahead of the oxide front in all cases. The shape and distribution of carbides and cavities in the plain of the cracked GBs was analyzed in 3D to gain a mechanistic understanding of the processes that may be leading to SCC initiation in highly CW alloy 690.

Key words: 3D FIB/SEM, Ni-base alloys, SCC initiation, cold-work, UNS N6690, (Alloy 690)

Product tags
Also Purchased
Picture for Effect of Strain Rate on the Crack Growth Rate of 718 Under Cathodic Potentials
Available for download

51317--9669-Effect of Strain Rate on the Crack Growth Rate of 718 Under Cathodic Potentials

Product Number: 51317--9669-SG
ISBN: 9669 2017 CP
Author: Thodla Ramgopal
Publication Date: 2017
$20.00

Crack growth rate (CGR) behavior of UNS N07718 was investigated as a function of K-rate in two different environments under cathodic potentials, a mild environment containing 3.5wt% NaCl and a more aggressive environment containing 0.5M H2SO4.

 
Picture for Effect of Cold Deformation on Sulfide Stress Cracking of High Strength Steels
Available for download

51317--9610-Effect of Cold Deformation on Sulfide Stress Cracking of High Strength Steels

Product Number: 51317--9610-SG
ISBN: 9610 2017 CP
Author: María José Cancio
Publication Date: 2017
$20.00

A quantitative assessment of remnant cold deformation and effectiveness of post deformation treatment (PDT) on sour resistance and mechanical properties of a C110 grade by reproducing uniform deformation with tensile/compressive tests followed by heating/soaking/cooling cycles representing induction PDT

 
Picture for Problems Related to the Slow Strain Rate Test Performance and the Specimen Characterization in Auste
Available for download

51317--9715-Problems Related to the Slow Strain Rate Test Performance and the Specimen Characterization in Austenitic Corrosion Resistant Alloy Tubes

Product Number: 51317--9715-SG
ISBN: 9715 2017 CP
Author: Pilar Esteban
Publication Date: 2017
$20.00

The specimen surface, effect of filling rate were examined. Characterization of the primary fracture surface and the gauge section of the tested specimens was done by scanning electron microscopy and subsequent classification according to the NACE TM0198 standard.
Categories
Industry
Recently viewed
Popular tags
View all

Association for Materials Protection and Performance

© AMPP All Rights Reserved.
Membership Terms of Content Use
Contact Customer Support