Effect of ZrB2 additions on the thermal stability of polycrystalline diamond

Abstract

This study investigates the effect of ZrB2 additions on the microstructure, thermal stability, and thermo-mechanical wear resistance of polycrystalline diamond. Following high-pressure high-temperature (HPHT) sintering, the ZrB2-PCD material binder phase consisted of cobalt-boride (Co2B and B6Co23) phases. In-situ PXRD and TEM vacuum annealing experiments observed that the onset of bulk graphitisation occurred above 1000 °C for the ZrB2-PCD material, compared to 850 °C for the STD-PCD material. The ZrB2-PCD tools showed excellent thermo-mechanical wear resistance, 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 ZrB2 additive phase content, mixing methodology, or sintering conditions could be explored to improve the abrasive wear resistance of this novel PCD material.