Tribological behaviour of alumina-based nanocomposites reinforced with uncoated and Ni-coated cubic boron nitride

Currently, there is a rising demand to develop composite materials with outstanding tribological properties along with excellent thermal-mechanical properties for harsh tribological applications. In view of this demand, the tribological behaviour of spark plasma sintered (SPS) nano-alumina (∼150nm)-based composites reinforced with 10, 20 and 30 wt.% uncoated and nickel-coated cubic boron nitride (cBN) particles was evaluated using a ball-on-disc configuration against three different counterface materials (WC, Si₃N₄ and Al₂O₃) under dry sliding conditions. A variety of techniques were used to evaluate the phase composition and to study the dispersion, wear behaviour and wear mechanisms. The nano-alumina composites exhibited improved wear resistance and coefficient of friction (COF). These results were attributed to the unique combination and uniform dispersion of the reinforcing particles within the composites. Moreover, Ni-coated cBN particles displayed high wear resistance, primarily due to the excellent interfacial bonding provided by the nickel coating. The wear resistance of the sample reinforced with 30% cBN-Ni was improved by at least 85%. The wear mechanisms involved during sliding wear were abrasion, matrix grain pullout (dislodgement of matrix material), microcracking, chipping, and tribolayer formation.