Mechanisms of stress-corrosion cracking of alloy X-750 in high-purity water

Journal Article · Sun Sep 01 04:00:00 EDT 1985 · J. Mater. Energy Syst.; (United States)

DOI:https://doi.org/10.1007/BF02833560· OSTI ID:6198732

Grove, C A; Petzold, L D

The high-strength, nickel-base alloy X-750 is susceptible to stress-corrosion cracking (SCC) in high-purity, deaerated water. Crack initiation occurs at high temperatures (>400F (204C)). Crack propagation occurs in both high-temperature and lowtemperature (<300F(149C)) water. High-temperature crack growth rates are on the order of mils per day. Low-temperature cracking is extremely rapid (approx. =100 in. (250 cm) per day). Three heat treatments of Alloy X-750 are investigated: stress equalized1625F (885C)/24 hours + 1300F (704C)/20 hours, direct aged-1300F (704C)/24 hours, and solution annealed and direct aged-2000F (1093C)/ 1 hour + 1300F (704C)/20 hours. 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.

• Research Organization: Knolls Atomic Power Laboratory, Schenectady, NY
• OSTI ID: 6198732
• Journal Information: J. Mater. Energy Syst.; (United States), Journal Name: J. Mater. Energy Syst.; (United States) Vol. 7:2; ISSN JMSMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103 -- Metals &amp; Alloys-- Mechanical Properties
360105* -- Metals &amp; Alloys-- Corrosion &amp; Erosion
ALLOYS
CARBIDES
CARBON COMPOUNDS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CORROSION
CORROSIVE EFFECTS
CRACK PROPAGATION
CRACKS
CRYSTAL STRUCTURE
ELEMENTS
EMBRITTLEMENT
FRACTURE PROPERTIES
GRAIN BOUNDARIES
HEAT TREATMENTS
HYDROGEN COMPOUNDS
HYDROGEN EMBRITTLEMENT
INCONEL ALLOYS
INCONEL X750
IRON ALLOYS
MECHANICAL PROPERTIES
METALLURGICAL EFFECTS
MICROSTRUCTURE
NICKEL ALLOYS
NICKEL BASE ALLOYS
NONMETALS
OXYGEN COMPOUNDS
PHOSPHORUS
SEGREGATION
STRESS CORROSION
STRESSES
TEMPERATURE EFFECTS
THERMAL STRESSES
TITANIUM ALLOYS
WATER