Effects of Hydrogen Concentration, Specimen Thickness and Loading Frequency on the Hydrogen Enhanced Crack Propagation of Low Alloy Steel

Abstract:

Crack propagation of SCM440H low alloy steel under varying load is enhanced by absorbed hydrogen. Substantial acceleration of crack propagation rate up to 1000 times was observed compared with that of uncharged material. The role of factors affecting enhanced acceleration was investigated by changing hydrogen concentration absorbed in metal, specimen thickness and loading frequency. Results are as follows. (1) 0.2 mass ppm diffusible hydrogen in metal was enough to cause enhanced acceleration. The predominant fracture mode showing acceleration was quasi cleavage. (2) In the case of thin specimen thinner than 0.8mm, the tri-axiality of stress is weak, and the enhanced crack propagation did not appear. However, the introduction of side-groove to 0.8mm specimen in order to increase the tri-axiality resulted in enhanced acceleration. (3) Lower loading frequency resulted in higher crack propagation rate in cycle domain. The crack propagation rate in time domain was almost constant irrespective of loading frequency. Enough concentration of hydrogen, tri-axiality and low loading frequency resulted in enhanced acceleration of fatigue crack propagation.

• Periodical: Key Engineering Materials (Volume 465)
• Pages: 519-522
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.465.519
• Online since: January 2011
• Authors: Yoshiyuki Kondo, Koshiro Mizobe, Masanobu Kubota
• Keywords: Fatigue Crack Propagation, Hydrogen Embrittlement, Low Alloy Steel

References

[1] Y. Kondo, M. Kubota and K. Shimada, Crack Propagation Behavior of SCM440H Low Alloy Steel Enhanced by Hydrogen under Long-term Varying Load and Static Load, Engineering Fracture Mechanics, Vol. 77, No. 11 (2010), p.1963-(1974).

DOI: 10.1016/j.engfracmech.2010.01.012