Some Aspects of the Fracture of WC-Co Composites

  • Frédéric Osterstock
  • Jean-Louis Chermant


During the last decade, fracture mechanics measurements on cemented carbides became of current use. Critical stress intensity factor values obtained in different laboratories with different specimen geometries show good agreement for similar batches (1) (2) (3) (4) (5). By this way it appeared that tungsten-carbide is rather tough if compared to other carbides (6) (7). Furthermore, this toughness can be increased by cobalt additions. Combination of critical stress intensity factor and rupture stress, mostly obtained in bending, allows one to evaluate the size of the critical defect, ac, i.e. the size of the initiating defect at the moment where crack propagation becomes catastrophic. The calculated values of ac are low compared to other carbides or single phased ceramics (7). This arises from liquid-phase sintering, however it shows clearly that mechanical strength of cemented carbide may be affected by very small defects like porosity or carbide crystal bundles... Influence of structural heterogeneities was already evidenced by S.B. Luyckx (8) when she noted that fracture origin is generally associated with the presence of impurities or inclusions. The statistical analysis of rupture made by P. Anderson (9) gave the same conclusion. H. Suzuki and K. Hayashi (10) made fractographic analyses of broken specimens, located the initiating defect and measured the size.


Stress Intensity Factor Cobalt Content Rupture Stress Binder Content Critical Stress Intensity Factor 
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Copyright information

© Plenum Press, New York 1983

Authors and Affiliations

  • Frédéric Osterstock
    • 1
  • Jean-Louis Chermant
    • 1
  1. 1.Equipe Matériaux Microstructure, Laboratoire de Cristallographie et Chimie du Solide, L.A. 251ISMRA-UniversitéCaen CedexFrance

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