  This study investigates the effect of ZrB$_2$ additions on the
microstructure, thermal stability, and thermo-mechanical wear behaviour of
polycrystalline diamond. Following high-pressure high-temperature (HPHT)
sintering, the ZrB$_2$-PCD material showed a full conversion of the binder
phase to cobalt-boride (Co2B and Co$_{23}$B$_6$) phases. In-situ PXRD and TEM
vacuum annealing experiments observed that the onset of bulk graphitisation
occurred above $1000^{\circ}C$ for the ZrB$_2$-PCD material, compared to
$850^{\circ}C$ for the STD-PCD material. The ZrB$_2$-PCD tools showed excellent
thermo-mechanical wear behaviour, exhibiting increased durability and a steady
wear scar progression during high-temperature dry-VTL testing. However, lowered
abrasion wear resistance was observed for the ZrB2-PCD tools during
low-temperature wet-VTL testing, probably due the reduced diamond contiguity in
the ZrB2 additive sample. Further optimisation of the ZrB$_2$ additive phase
content, mixing methodology, or sintering conditions could be explored to
improve the abrasive wear resistance of this novel PCD material.
