Abstract
In WC-Co cemented carbides operating under conditions of cyclic temperature variations the nucleation and propagation of thermal fatigue cracks are caused by high stresses that arise due to the great difference in thermal expansion coefficients between the WC grains and the cobalt binder phase. The present investigation, which is based on laboratory tests where a ceramic pin is pressed against a rotating carbide ring, has been carried out with the aim of elucidating the influence of the cobalt content and the WC grain size on the propagation rate of thermal fatigue cracks. The rate-controlling factor is shown to be the width of the binder phase interlayers between adjacent carbide grains, and this is explained by taking into account the distribution of stacking faults and partial dislocations in the binder phase in the as-sintered condition.
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