Abstract
Wear and friction properties of Al2O3 composite reinforced with in-situ formed aluminum borate (9Al2O3·2B2O3) and hexa-boron nitride (h-BN) have been investigated. The initial constituents for the composites were Al2O3, AlN, and H3BO3. The H3BO3 was used as a source of B2O3, where B2O3 reacted with AlN and Al2O3 to form in-situ h-BN and 9Al2O3·2B2O3. Based on the thermodynamic calculation and phase transformation, four different compositions were selected. First, the powders were mixed by ball milling followed by compaction at 10 MPa. The compacted pellets were sintered at 1400 °C in vacuum. The composites were characterized using X-ray diffraction followed by hardness measurement and reciprocating sliding test against alumina and steel balls. The X-ray diffraction results revealed the formation of in situ phases of 9Al2O3·2B2O3 and h-BN that improved the tribological properties. By comparing the tribological performance of different composites, it was found that the hard 9Al2O3·2B2O3 phase maintains the wear resistance of composites, whereas the coefficient of friction is highly dependent on the counter ball. Against alumina ball, the lowest coefficient of friction was observed for the composites with maximum h-BN concentration and minimum aluminum borate concentration, whereas the opposite trend was observed against the steel ball.
Highlights
Ceramic materials are potential candidates for wear-resistance components because of their hardness, corrosion resistance, and high-temperature stability
The low-density alumina-based composite was successfully synthesized with the in-situ formation of aluminum borate and Hexagonal boron nitride (h-BN) phase
It was observed that the formation of aluminum borate helps to achieve a lower density of the composite and reduces the wear rate due to its hardness
Summary
Ceramic materials are potential candidates for wear-resistance components because of their hardness, corrosion resistance, and high-temperature stability. Their tribological applications are restricted by their poor lubricating property. To overcome the poor lubricity, solid lubricants, such as graphite [1,2], graphene [3,4], MoS2 [5], and CaF2 [6], are used in ceramic matrixes to form a self-lubricating ceramic composite with improved tribological properties. Alumina is one of the most employed ceramic materials, showing an excellent combination of properties that includes a high melting point, hardness, and corrosion resistance. Hexagonal boron nitride (h-BN) is one of the potential solid lubricants that has been used for synthesizing self-lubricating composites.
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