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 behaviour of polycrystalline diamond. Following high-pressure high-temperature (HPHT) sintering, the ZrB2-PCD material showed a full conversion of the binder phase to cobalt-boride (Co2B and Co23B6) phases. In-situ PXRD and TEM vacuum annealing experiments observed that the onset of bulk graphitisation occurred above 1000C for the ZrB2-PCD material, compared to 850C for the STD-PCD material. The ZrB2-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 ZrB2 additive phase content, mixing methodology, or sintering conditions could be explored to improve the abrasive wear resistance of this novel PCD material.