Journal of Failure Analysis and Prevention

, Volume 15, Issue 4, pp 513–520 | Cite as

Cracking Failure of Locomotive Diesel Engine Injector Nozzles

  • Xiao-lei Xu
  • Zhi-wei Yu
Technical Article---Peer-Reviewed


Two locomotive diesel engine injector nozzles fractured during service. The fractured injector nozzles are fabricated with 18CrNi8 steel, and the external and the internal surfaces of injector nozzles are required to be carburized. Visual inspections indicate that the fracture occurred just at the transition fillet root between the large excircle and the secondary excircle of injector nozzle. Fractographic investigation indicates that the crack origin is situated at the oil-filled groove with a thin wall thickness and the brittle intergranular fracture is the main failure mode of the two injector nozzles. Metallurgical examinations show that case depths through the entire wall thickness are present at the fracture regions. The brittle microstructure typical of carburized layer was produced in the fracture regions, which was confirmed by the occurrence of intergranular micro-cracks. The presence of case depth through the entire wall thickness in the fracture region made the toughness at the region decrease intensely. The crack initiated at the weakened location and propagated from the internal surface toward the external surface under the impact of the oiling pressure with high-frequency pulsation to lead to transverse brittle fracture of the two injector nozzles. Additionally, the presence of many brittle Al2O3 complex inclusions in the vicinity of the fracture region induced tensile stress in the matrix around inclusions and the stress concentration around the inclusions to promote initiation of the crack.


Injector nozzle Brittle fracture Carburizing Case depth Inclusion 



The project is supported by “the Fundamental Research Funds for the Central Universities (No. 3132014323)”.


  1. 1.
    ASM Handbook, Heat Treating, vol. 4. (ASM International, Materials Park, 1991)Google Scholar
  2. 2.
    China National Standardization Committee, Determination of Carburized Depth and Metallurgic Examination of Carburizing Structure (GB9540, Chinese Standard, 1994) (in Chinese)Google Scholar
  3. 3.
    J.D. Varin, Fracture characteristics of steering gear sector shafts. Pract. Fail. Anal. 2(4), 65–69 (2002)CrossRefGoogle Scholar
  4. 4.
    G. Straffelini, L. Versari, Brittle intergranular fracture of a thread: the role of a carburizing treatment. Eng. Fail. Anal. 16, 1448–1453 (2009)CrossRefGoogle Scholar
  5. 5.
    Tezcan Sekercioglu, Failure study of pneumatic rock drill piston. Eng. Fail. Anal. 13, 1108–1115 (2006)CrossRefGoogle Scholar
  6. 6.
    Osman Asi, Failure of a diesel engine injector nozzle by cavitation damage. Eng. Fail. Anal. 13, 1126–1133 (2006)CrossRefGoogle Scholar
  7. 7.
    Haoxuan Cui, Weiqiang Wang, Aiju Li, Mengli Li, Xu Shugen, Huadong Liu, Failure analysis of the brittle fracture of a thick-walled 20 steel pipe in an ammonia synthesis unit. Eng. Fail. Anal. 17, 1359–1379 (2010)CrossRefGoogle Scholar
  8. 8.
    M.R. Krishnadev, S.C. Jain, Improved productivity through failure analysis: Case studied in precision forging of aerospace components. Eng. Fail. Anal. 14, 1053–1064 (2007)CrossRefGoogle Scholar

Copyright information

© ASM International 2015

Authors and Affiliations

  1. 1.Key Laboratory of Ship-Machinery Maintenance & Manufacture Ministry of Communication, Department of Materials Science and EngineeringDalian Maritime UniversityDalianP.R. China

Personalised recommendations