Journal of Failure Analysis and Prevention

, Volume 10, Issue 4, pp 312–321 | Cite as

Failure Analysis of WC–2Ni–1Co Rotor Part

Technical Article---Peer-Reviewed

Abstract

This study deals with the analysis of an ink-producing machine rotor part composed of WC–2Ni–1Co which failed in brittle manner during service. The part was made by powder metallurgy techniques and is being used in ink-grinding machines due to its high hardness and wear resistance. Similar parts had worked satisfactorily for many ink compositions, but the part under investigation failed prematurely. Investigation was considered important because the part is expensive, and other identical components frequently failed after a short service life. Moreover, replacement of the part requires complete dismantling of the machine which reduces the production rate. Spectroscopic analysis, density, optical and scanning electron microscopy, SEM–EDS analysis, fractography, X-ray diffraction, and microhardness measurements were carried out on failed parts to find out the root causes of the failure. Results revealed that the part cracked due to combined effects of selective dissolution of metal binder-caused corrosive action of ink solution and hydrogen-induced deterioration of WC and Ni–Co phases. Localized removal of binder phase left the hard WC phase unsupported. Cracks were found initiating from the root of the machined slot which acted as a stress concentration point and resulted in brittle fracture.

Keywords

WC–Co Brittle fracture Embrittlement Fractography Corrosion Dissolution Microhardness 

Notes

Acknowledgments

The authors thank Mr. Sajid Ali Asghar for XRF analysis, and Mr. Zahid of Materials Engineering Department for optical microscopy. The authors also thank Mr. Yousuf Khan (Centralize Science Laboratory, Karachi University) for providing SEM–EDS facility, and Mr. Sheikh Kamal-ud-din (PCSIR Laboratories, Karachi) for providing XRD facility.

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Copyright information

© ASM International 2010

Authors and Affiliations

  • M. Faraz
    • 1
  • Fawad Tariq
    • 1
  • Ashraf Ali
    • 1
  • Nausheen Naz
    • 2
  1. 1.Materials Engineering DepartmentNED University of Engineering and TechnologyKarachiPakistan
  2. 2.Mechanical Engineering DepartmentNED University of Engineering and TechnologyKarachiPakistan

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