Influences of gaseous environment on low growth-rate fatigue crack propagation in steels. Annual report No. 1, January 1980. Report No. FPL/R/80/1030

Technical Report · Tue Jan 01 04:00:00 EST 1980

DOI:https://doi.org/10.2172/5157733· OSTI ID:5157733

Ritchie, R O; Suresh, S; Toplosky, J

The influence of gaseous environment is examined on fatigue crack propagation behavior in steels. Specifically, a fully martensitic 300-M ultrahigh strength steel and a fully bainitic 2-1/4Cr-1Mo lower strength steel are investigated in environments of ambient temperature moist air and low pressure dehumidified hydrogen and argon gases over a wide range of growth rates from 10/sup -8/ to 10/sup -2/ mm/cycle, with particular emphasis given to behavior near the crack propagation threshold ..delta..K/sub 0/. It is found that two distinct growth rate regimes exist where hydrogen can markedly accelerate crack propagation rates compared to air, (1) at near-threshold levels below (5 x 10/sup -6/ mm/cycle) and (2) at higher growth rates, typically around 10/sup -5/ mm/cycle above a critical maximum stress intensity K/sub max//sup T/. Hydrogen-assisted crack propagation at higher growth rates is attributed to a hydrogen embrittlement mechanism, with K/sub max//sup T/ nominally equal to K/sub Iscc/ (the sustained load stress corrosion threshold) in high strength steels, and far below K/sub Iscc/ in the strain-rate sensitive lower strength steels. Hydrogen-assisted crack propagation at near-threshold levels is attributed to a new mechanism involving fretting-oxide-induced crack closure generated in moist (or oxygenated) environments. The absence of hydrogen embrittlement mechanisms at near-threshold levels is supported by tests showing that ..delta..K/sub 0/ values in dry gaseous argon are similar to ..delta..K/sub 0/ values in hydrogen. The potential ramifications of these results are examined in detail.

• Research Organization: Massachusetts Inst. of Tech., Cambridge (USA). Dept. of Mechanical Engineering
• DOE Contract Number: AC02-79ER10389
• OSTI ID: 5157733
• Report Number(s): DOE/ER/10389-1
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
AIR
ALLOYS
ARGON
ATMOSPHERES
CHROMIUM ALLOYS
CHROMIUM STEELS
CHROMIUM-MOLYBDENUM STEELS
CONTROLLED ATMOSPHERES
CRACKS
CRYOGENIC FLUIDS
ELEMENTS
EMBRITTLEMENT
FATIGUE
FLUIDS
GASES
HYDROGEN
HYDROGEN EMBRITTLEMENT
IRON ALLOYS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
METALLURGICAL EFFECTS
MOBILITY
NONMETALS
RARE GASES
STEELS