Journal of Failure Analysis and Prevention

, Volume 9, Issue 1, pp 43–48 | Cite as

Failure Analysis of Cracked Gear Shafts

  • Zhi-wei Yu
  • Xiao-lei Xu
Case History


Two gear shafts cracked during the fabrication. The cracks are through the grooves associated with the gear teeth and propagated completely across the shaft. Fractography on the cracked teeth indicates that the crack origins are about 3.5 to 4.0 mm from the groove and exhibit pointlike features. Fracture surfaces near the crack origin regions were intergranular, and the fracture appeared to have occurred instantaneously. Metallurgical analysis indicates that decarburization had occurred on the surfaces of the gear shafts, but occurrence of decarburization has no relation to the cracking. Cracking occurred during the carburization-quenching process and originated at a cluster of Al2O2 complex inclusions. The thermal stress produced by quenching drove the cracking process.


Gear shaft Failure analysis Instantaneous cracking Inclusion clusters Decarburization 


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Copyright information

© ASM International 2008

Authors and Affiliations

  1. 1.Electromechanics and Material Engineering CollegeDalian Maritime UniversityDalianP.R. China

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