Microbe-enhanced environmental fatigue crack propagation in HY130 steel
- Univ. of Virginia, Charlottesville, VA (United States). Dept. of Materials Science and Engineering
Research was undertaken to characterize the effect of sulfate-reducing bacteria (SRB) on aqueous environment-enhanced fatigue cracking in a high-strength alloy steel. Desulfovibrio vulgaris in Postgate C solution greatly increased rates of ambient-temperature fatigue crack propagation (FCP) in tempered martensitic HY130 steel (MIL-S-24371A) under cathodic polarization and low-frequency, constant stress intensity range ([Delta]K) loading. Crack growth rates (da/dN) in the SRB solution increased 50- to 1,000-fold relative to FCP in sterile sodium chloride (NaCl) solution at [minus]1,000 mV[sub SCE] and under vacuum, respectively. The presence of microbes shifted fatigue cracking from a transgranular path (typical in sterile NaCl) to an intergranular crack path consistent with the enhanced growth rates. The SRB reduced fatigue crack initiation resistance, countering the beneficial effect of cathodic polarization for sterile NaCl. Metal embrittlement and increased hydrogen uptake at the occluded crack tip caused by bacterially produced hydrosulfide (HS[sup [minus]]) and sulfide (S[sup 2[minus]]) ions were implicated. SRB did not appear to colonize the occluded alkaline crack tip. At constant [Delta]K, transient environmental FCP in the SRB solution was substantial and was most likely a result of time-dependent bacterial growth and enhanced metabolically produced sulfides. Other time-dependent hydrogen sources may have been important.
- OSTI ID:
- 7108693
- Journal Information:
- Corrosion (Houston); (United States), Journal Name: Corrosion (Houston); (United States) Vol. 50:5; ISSN 0010-9312; ISSN CORRAK
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360103* -- Metals & Alloys-- Mechanical Properties
360105 -- Metals & Alloys-- Corrosion & Erosion
560300 -- Chemicals Metabolism & Toxicology
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ALLOYS
BACTERIA
BIOLOGICAL FOULING
CATHODIC PROTECTION
CHEMICAL REACTIONS
CORROSION
CORROSION PROTECTION
CORROSIVE EFFECTS
CRACK PROPAGATION
DESULFOVIBRIO
EMBRITTLEMENT
FOULING
HYDROGEN EMBRITTLEMENT
INTERGRANULAR CORROSION
IRON ALLOYS
IRON BASE ALLOYS
MARTENSITIC STEELS
MICROORGANISMS
STEELS
STRESS INTENSITY FACTORS
SULFATE-REDUCING BACTERIA