Susceptibility of cold-worked zirconium-2. 5 wt. percent niobium alloy to delayed hydrogen cracking

Technical Report · Thu Jan 01 04:00:00 EST 1976

OSTI ID:7220094

Coleman, C E

Notched tensile specimens of cold-worked zirconium--2.5 wt. percent niobium alloy were stressed at 350 and 520 K. At 350 K, above a possible threshold stress of 200 MPa, specimens exhibited delayed failure which was attributed to hydride cracking. Metallography showed that hydrides accumulated at notches and tips of growing cracks. The time to failure appeared to be independent of hydrogen content over the range 7 to 100 ppM hydrogen. Crack growth rates of about 10/sup -10/ m/s deduced from fractography were in the same range as those necessary to fracture pressure tubes. The asymptotic stress intensity for delayed failure, K/sub 1H/, appeared to be about 5 MPa/m/sup 2/. With this low value of K/sub 1H/ small surface flaws may propagate in pressure tubes which contain large residual stresses. Stress relieving and modified rolling procedures reduce the residual stresses to such an extent that only flaws 12 percent of the wall thickness or greater grow. At 520 K no failures were observed at times a factor of three greater than times to failure at 350 K. Zirconium--2.5 wt. percent niobium appears to be safe from delayed hydrogen cracking at the reactor operating temperature.

• Research Organization: Atomic Energy of Canada Ltd., Chalk River, Ontario. Chalk River Nuclear Labs.
• OSTI ID: 7220094
• Report Number(s): N-77-11156; AECL-5260
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
220200 -- Nuclear Reactor Technology-- Components & Accessories
36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
ALLOYS
COLD WORKING
CRACKS
CRYOGENIC FLUIDS
ELEMENTS
EMBRITTLEMENT
FABRICATION
FLUIDS
HIGH TEMPERATURE
HYDROGEN
MATERIALS WORKING
MEDIUM TEMPERATURE
METALLURGICAL EFFECTS
NIOBIUM ALLOYS
NONMETALS
REACTOR MATERIALS
VERY HIGH PRESSURE
ZIRCONIUM ALLOYS
ZIRCONIUM BASE ALLOYS