A study was conducted of the effect of nonmetallic inclusions on the fatigue and corrosion fatigue resistance of a high-strength steel in 0.6 M sodium chloride (NaCl) solutions. Results indicated that angular calcium-aluminate inclusions played an important role in introducing cracks during air fatigue cycling; however, sulfide inclusions appeared to be the main contributors to sites for corrosion pits and subsequent crack initiation. Conventional consideration based on the stress intensification caused by such defects was insufficient to describe the role of nonmetallic inclusions in fatigue crack development in air and by corrosion pits during corrosion fatigue. However, it was considered that the interaction between geometric discontinuities (i.e., nonmetallic inclusions and cyclic loading) resulted in plasticity localization and, thus, facilitated crack development. Similarly, enhancement of localized dissolution resulting from plasticity localization contributed to corrosion pit development at nonmetallic inclusion sites, thus promoting early crack development when a corrosive environment was presented.

Subject
Pits, Environmental cracking, Corrosion fatigue, Materials, Crack initiation, Corrosion cracking, Stress cracking, Stress, Sodium chloride solution, Steel, Pitting, Fatigue, Inclusions
Keywords:
cracking, dissolution, fatigue, high-strength steel, inclusions, pitting, plasticity localization, sodium chloride
NACE International
1996
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