Mechanism of stress-corrosion cracking of Alloy X-750 in high purity water
The high strength Ni-base Alloy X-750 is susceptible to stress-corrosion cracking (SCC) in high purity, deaerated water. Crack initiation occurs at high temperatures (>400F). Crack propagation occurs in both high-temperature and low-temperature (<300F) water. High-temperature crack growth rates are on the order of mils/day. Low-temperature cracking is extremely rapid (approx.100 in./day). Three heat treatments of Alloy X-750 are investigated: (1) Stress Equalized - 1625F/24 hr + 1300F/20 hr, (2) Direct Aged - 1300F/24 hr, and (3) Solution Annealed and Direct Aged - 2000F/1 hr + 1300F/20 hr. Stress-equalized Alloy X-750 is most susceptible to SCC; solution-annealed and direct-aged Alloy X-750 is least susceptible. A Hydrogen Embrittlement Model of SCC is developed that predicts SCC performance on the basis of grain boundary chemistry and grain boundary carbides. Phosphorus segregates to the grain boundary in concentrations of up to approx.100 times the bulk concentration during processing and heat treatment. Phosphorus at the grain boundaries increases susceptibility to high- and low-temperature SCC. The presence of M23C6-type carbides and/or the absence of MC-type carbides at the grain boundaries improves SCC performance in high-temperature water. 18 figs., 5 tabs.
- Research Organization:
- Knolls Atomic Power Lab., Schenectady, NY (USA)
- DOE Contract Number:
- AC12-76SN00052
- OSTI ID:
- 6218844
- Report Number(s):
- KAPL-4186; CONF-8410208-3; ON: DE86006361
- Resource Relation:
- Conference: ASM international conference on corrosion of nickel base alloys, Cincinnati, OH, USA, 23 Oct 1984; Other Information: Portions of this document are illegible in microfiche products. Original copy available until stock is exhausted
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
INCONEL X750
STRESS CORROSION
CRACK PROPAGATION
FAILURES
FRACTURES
GRAIN BOUNDARIES
HEAT TREATMENTS
MICROSTRUCTURE
ALLOYS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CORROSION
CRYSTAL STRUCTURE
INCONEL ALLOYS
IRON ALLOYS
NICKEL ALLOYS
NICKEL BASE ALLOYS
TITANIUM ALLOYS
360105* - Metals & Alloys- Corrosion & Erosion