Enhanced wear resistance in AlMgB14–TiB2 composites

Studies of bulk AlMgB14 and TiB2 composites have shown that these materials exhibit exceptional resistance to erosive and abrasive wear. Multi-hour ASTM erosion tests with Al2O3 abrasive against composite samples comprised of AlMgB14 (40 vol.%) and TiB2 (60 vol.%) resulted in erosion rates of 0.5 mm3/kg of erodent, compared with 10.5 mm3/kg for wear-resistant grades of WC–6% Co. Increasing the TiB2 fraction to 80 vol.% further reduced erosion rates to as low as 0.26 mm3/kg. Fracture nucleation in the TiB2 grains was identified by SEM analysis as a primary damage mechanism. Additionally, diamond abrasion testing revealed a slightly different trend between composition and wear than that observed in erosion testing. Results of wear tests are discussed in terms of microstructure, hardness and indentation toughness of each phase, and grain boundary cohesion. Analysis suggests several energy dissipative mechanisms including fracture termination at grain boundaries and conversion of mechanical energy to thermal energy act to improve wear resistance in the fine-grained boride composites.