Journal of Failure Analysis and Prevention

, Volume 13, Issue 1, pp 8–19 | Cite as

An Environmentally Assisted Cracking Evaluation of UNS C64200 (Al–Si–Bronze) and UNS C63200 (Ni–Al–Bronze)

  • Michelle Koul
  • Jennifer Gaies


A recent failure of a union nut, UNS C64200, made of Al–Si–Bronze (ASB) in a breathing air system of a marine platform has highlighted the need for environmentally assisted cracking (EAC) data for both ASB and Ni–Al–Bronze UNS C63200 (NAB) components in environments relevant to marine use. In addition, the possibility of exposure to ammonia environments via cleaning agents or biological processes warrants consideration because of the known susceptibility of bronze to EAC in ammonia environments. A displacement-controlled, rising step load (RSL) technique was employed on precracked compact tension specimens to quantify and compare the threshold stress intensities for EAC in air, seawater (SW), and SW + ammonia environments for wrought ASB and NAB materials. These results are compared to calculations of the stress intensity in service to determine the probability of EAC initiation. ASB was found to be susceptible to subcritical intergranular EAC initiation in laboratory air, SW, and SW + ammonia environments. NAB was immune to EAC under the conditions tested in laboratory air and SW, but was susceptible to intergranular EAC in SW + ammonia solution. The threshold stress intensity in SW + ammonia was found to be similar for both ASB and NAB; however, the subcritical crack growth rate for NAB was found to be 2–3 times faster than ASB. Calculations of stress intensity indicate that, in the air system applications where the installation torques are higher, the likelihood of subcritical cracking in ammonia environments is high. Stress intensities approach the ASB threshold values for subcritical intergranular cracking in air when the defect depth approaches half the wall thickness of the nut.


Cracking behavior Environmentally assisted cracking SEM Stress corrosion cracking Nonferrous metals Bronze Ammonia 



The authors would like to thank Mr. A. Brandemarte of NSWCCD Code 612 for preparing metallographic samples. In addition, the authors would like to thank Mr. A. Leofsky and Mr. F. Kachele of NSWCCD Code 612, Mr. M. Worris of SEA 05Z4, and Mr. J. Hungerbuhler of NSWCCD-SSES 9240 for their useful background information and discussions of union nut service applications.


  1. 1.
    Copper Development Association Publication No. 80, Aluminum Bronze Alloy Corrosion Resistance Guide, (1981)Google Scholar
  2. 2.
    Standard Specification for Aluminum Bronze Rod, Bar and Shapes, B150/B150M, American Society for Testing and Materials, vol. 02.01, 2008Google Scholar
  3. 3.
    Leofsky, A.: Failure analysis of USS San Antonio (LPD-17) No. 3 Breathing Air Flask Union Nut, Memorandum Ser 612/10-083, NSWCCD, West Bethesda, MD, 2010Google Scholar
  4. 4.
    Phoplonker, M., Byrne, J., Duggan, T., Scheffel, H., Barnes, P.: Near-threshold fatigue crack growth in an aluminum bronze alloy. In: International Conference on Fatigue of Engineering Materials and Structures, vol. I, 15–19 Sept 1986, University of Sheffield. IMechE Conference Publications C277/86, University of SheffieldGoogle Scholar
  5. 5.
    Private Communication, NAVSEA 05Z41 (Worris) and NSWCCD-SSES 9240 (Hungerbuhler) of 6 Oct 2011Google Scholar
  6. 6.
    Lynch, S.P., Edwards, D.P., Nethercott, R.B., Davidson, J.L.: Failure of nickel–aluminum bronze hydraulic couplings, with comments on general procedures for failure analysis. Pract. Fail. Anal. 2(6), 50–61 (2002)Google Scholar
  7. 7.
    Fonlupt, S., Bayle, B., Delafosse, D., Heuze, J.: Role of second phases in the stress corrosion cracking of a nickel–aluminum bronze in saline water. Corros. Sci. 47, 2792–2806 (2005)CrossRefGoogle Scholar
  8. 8.
    Standard Test Method for Measurement of Hydrogen Embrittlement Threshold in Steel by the Incremental Step Loading Technique, F1624-09, American Society for Testing and Materials, vol. 15.03, 2009Google Scholar
  9. 9.
    Corrosion of Metals and Alloys—Stress Corrosion Testing, Part 9: Preparation and Use of Pre-Cracked Specimens for Tests Under Rising Load or Rising Displacement, ISO 7539-9, International Standard, 2003Google Scholar
  10. 10.
    Standard Test Method for Measurement of Fracture Toughness, E1820-11, American Society for Testing and Materials, vol. 03.01, 2011Google Scholar
  11. 11.
    Standard Terminology Relating to Fatigue and Fracture Testing, E1823-11, American Society for Testing and Materials, vol. 03.01, 2011Google Scholar
  12. 12.
    Standard Practice for the Preparation of Substitute Ocean Water, ASTM D1141-08, American Society for Testing and Materials, vol. 11.02, 2008Google Scholar
  13. 13.
    Scheffel, R., Phoplonker, M., Byrne, J., Jones, R.L., Barnes, P.: Sustained load crack growth in an aluminum–silicon bronze alloy, fracture control of engineering structures. In: Van Elst, H., Bakker, A. (eds.) 6th European Conference on Fracture (ECF6), pp. 1851–1860. Amsterdam (1986)Google Scholar
  14. 14.
    Naval Sea Systems Command Standard Drawings 803-1385943 and 803-1385884, Naval Surface Warfare Center, Carderock Division—Ship Systems Engineering Station, West Bethesda, MD, 22 July 2008Google Scholar
  15. 15.
    Submarine Maintenance Engineering, Planning and Procurement, COMFLTFORCOMINST 4790.3 REVISION B CHANGE 3, Joint Fleet Maintenance Manual, vol. V, U.S. NavyGoogle Scholar
  16. 16.
    Juvinall, R., Marshek, K.: Fundamentals of Machine Component Design, 3rd edn, pp. 401–404. Wiley, New York (2000)Google Scholar
  17. 17.
    Riley, W., Sturges, L., Morris, D.: Mechanics of Materials, 5th edn, p. 252. Wiley, New York (1999)Google Scholar
  18. 18.
    Spence, J., Tooth, A.: Pressure Vessel Design: Concepts and Principles, p. 19. Taylor & Francis, Routledge (1994)Google Scholar
  19. 19.
    Moulick, S., Sahu, Y.: Stress intensity factor for internal cracks in thick walled pressure vessels using weight function technique. In: Proceedings from the National Conference on Innovative Paradigms in Engineering and Technology (NCIPET-2012), Int. J. Comput. Appl., 2012, pp. 6–12Google Scholar
  20. 20.
    Raju, I., Newman, J.: Stress-intensity factors for internal and external surface cracks in cylindrical vessels. J. Press. Vessel Technol. 104, 293–298 (1982)CrossRefGoogle Scholar

Copyright information

© ASM International 2012

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringUnited States Naval AcademyAnnapolisUSA
  2. 2.Naval Surface Warfare Center Carderock DivisionMetallurgy & Fasteners BranchWest BethesdaUSA

Personalised recommendations