Intergranular failures of Alloy 600 in high temperature caustic environments
This paper describes the results of our investigation of two commonly observed modes of failure of Alloy 600 in high temperature caustic environment namely, intergranular stress corrosion cracking (IGSCC) and intergranular attack (IGA). Specimens are studied as C-rings under constant deflection, wires with and without any externally applied load, and as straining electrodes. The potential dependence of average crack propagation rate is established in a single test by using several C-rings held at different potentials, by using a modification of the static potential gradient method of Seys and Van Haute. SCC appears to be governed by a film rupture mechanism and its propagation rate is significantly influenced by the electrochemical potential and associated surface film formation. The maximum crack propagation rate for C-rings and constant load specimens is very similar but much smaller than that calculated for a straining electrode at the same potential. IGA occurs over a wide range of potential - starting from a few tens of millivolts cathodic to the corrosion potential up to the lower end of anodic potentials normally required for SCC. IGA seems to be rather independent of stress and is generally more pronounced in the crevice area under the nuts used in C-rings. Examination of several creviced coupons shows that outside the crevice, enrichment of iron and chromium occurs on the surface as the potential is raised anodically, whereas the Ni:Fe and Ni:Cr ratios remain relatively independent of potential within the crevice.
- Research Organization:
- Brookhaven National Lab., Upton, NY (USA)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 6973801
- Report Number(s):
- BNL-34595; CONF-840405-12; ON: DE84010890
- Resource Relation:
- Conference: NACE corrosion '84 international forum and exhibition, New Orleans, LA, USA, 1 Apr 1984; Other Information: Portions are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
INCONEL 600
CREVICE CORROSION
INTERGRANULAR CORROSION
STRESS CORROSION
AQUEOUS SOLUTIONS
CRACK PROPAGATION
ELECTRIC POTENTIAL
FAILURE MODE ANALYSIS
SODIUM HYDROXIDES
TUBES
ALKALI METAL COMPOUNDS
ALLOYS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CORROSION
DISPERSIONS
HYDROGEN COMPOUNDS
HYDROXIDES
INCONEL ALLOYS
IRON ALLOYS
MIXTURES
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM ALLOYS
OXYGEN COMPOUNDS
SODIUM COMPOUNDS
SOLUTIONS
SYSTEM FAILURE ANALYSIS
SYSTEMS ANALYSIS
360105* - Metals & Alloys- Corrosion & Erosion