Wear mechanisms of diamond-containing hardmetals in comparison with diamond-based materials

The abrasion resistance of diamond/WC based hardmetal composites (commonly referred to as “diamond enhanced carbide”, or “DEC”) has been evaluated relative to those of a group of more conventional WC-Co materials and diamond (both polycrystalline and CVD) materials. Abrasion resistance, evaluated by means of the widely reported ASTM B611 test, was complimented by simulated field drilling trials, using a fine-grain quartzite, in the laboratory. This approach was taken as the drill test format has wider acceptance than another (complimentary) laboratory test, whether standardised, or bespoke, amongst end-users. In abrasion tests, polycrystalline and CVD diamond materials performed best, with the DEC materials being on a par with their conventional WC-Co counterparts. This behaviour was explained by the fact that the diamond in the composite (DEC) materials was readily plucked out of the wear surface, due to the aggressive nature of the B611 test. However, percussive drilling tests proved more encouraging, as the extent of diamond pluckout in DEC was not as widespread as in ASTM B611. Also, on the drill bit DEC insert surface, rock fragments were found to adhere to it, which appeared to have mitigated the severity of the prevailing wear regime somewhat.