Tribological properties of aluminum alloy matrix TiB2 composite prepared by in situ processing

An investigation of the wear behavior, in lubricated sliding and rolling of in situ prepared TiB₂ particle-reinforced 2024 T4 Al alloy matrix composites against 52100 steel and hardened pearlitic nodular cast iron, respectively, was undertaken. In sliding contact, the 10 vol pct 0.3-μm TiB₂-metal matrix composite (MMC) showed slightly less wear than the 10 vol pct 1.3-μm TiB₂-MMC. Transmission electron microscopy of cross sections, taken normal to the wear track and parallel to the sliding direction, revealed that the TiB₂ particles on the wear track were polished and particle pullout was largely absent. This was attributed to the strong interfacial bonding between the Al-alloy matrix and the TiB₂ reinforcing phase. The TiB₂ particles on the wear track inhibited spalling. Subsurface damage of the MMC did not occur. The wear of the steel mating surfaces worn against the TiB₂-MMCs was minor and caused by the cutting action of the TiB₂ particles that resided on the MMC wear track. In rolling contact, the 0.3-μm-size TiB₂-MMC showed 5 times higher weight loss than the 1.3-μm TiB₂-MMC for the same content of reinforcement, but the weight loss of the cast iron mating surface was less for the former. For the smaller particle size, the wear of 5 and 10 vol pct TiB₂-MMCs was the same. A high density of surface cracks was present on the wear track of the 0.3-μm TiB₂-MMC but not on the 1.3-μm MMC. The significance of strong particle/matrix interfacial bonding and particle size effect on the wear behavior of ceramic particulate-reinforced MMCs in lubricated sliding and rolling wear is discussed.