LAUSR

Some WC/Co hardmetal dies used for the high-temperature, high-pressure fabrication of polycrystalline diamond have been subjected to fractographic investigation after service failure. In each die a number of flat plate-like fragments have been found showing an unusual fountain-like appearance to the fracture surface markings. Despite extensive probing, discrete fracture origins could not be found. Instead, from the evidence of the microcracking found in the die bore region and the recognised development of deformations during a campaign, it was concluded that microstructural damage was developed under the complex non-equitriaxial compression stresses which are developed during the duty cycles. When the propagation of this damage reached the axial tensile zone that exists in the cooler regions of the die, the plate-like, more-brittle failure pattern developed.