Stress corrosion cracking in low-pressure steam turbines --An overview
- Southwest Research Inst., San Antonio, TX (United States)
This paper presents an overview of stress corrosion cracking (SCC) in low-pressure (LP) turbine discs through 1993. Disc cracking experience in power plants and pertinent results of research programs are summarized. Analyses of field experiences and laboratory studies conducted in the United Kingdom, the United States, and other countries showed that stress corrosion cracking of LP turbine disc steels can occur in pure condensed steam or pure water, as well as in known cracking environments, such as hot hydroxide solutions. It has been established that stress corrosion crack initiation in LP turbine disc steels exposed to high-purity water environments typical of those found in nuclear power plants depends upon seven factors: the presence of a liquid phase; the oxygen concentration of the liquid phase (or the electrode potential corresponding to the oxygen concentration); the yield strength of the steel used in discs; the disc temperature; tensile stress level; crevices and localized corrosion within crevices; and a combination of tensile stress and a flaw of size and shape sufficient to produce a K{sub I} value greater than K{sub ISCC}. While stress corrosion crack initiation depends upon the several factors listed above, the growth rate of stress corrosion cracks in LP turbine disc steels exposed to high-purity water and steam environments depends upon only three factors: the presence of a liquid phase; disc yield strength; and disc temperature. Importantly, stress corrosion crack growth rates in LP turbine disc steels are essentially independent of tensile stress level and stress intensity. Increase in both yield strength and temperature result in increased crack growth rate. 37 refs.
- OSTI ID:
- 70134
- Report Number(s):
- CONF-940222--
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
CRACK PROPAGATION
CREVICE CORROSION
DATA
FOSSIL-FUEL POWER PLANTS
MECHANICAL PROPERTIES
NUCLEAR POWER PLANTS
STEAM TURBINES
STEEL-CR2MO
STEEL-CR2MOV
STEEL-NI3CRMO
STEEL-NI3CRMOV
STEEL-NI4
STRESS CORROSION
UNITED KINGDOM
USA
WATER CHEMISTRY
WATER COOLED REACTORS