Transient liquid-phase assisted spark-plasma sintering and dry sliding wear of B4C ceramics fabricated from B4C nanopowders

With the motivation of developing B4C composites with superior wear resistance for tribological applications, an ultrafine-grained (similar to 200-300 nm) B4C composite was fabricated, characterized microstructurally, and tested mechanically and tribologically. First, a well-dispersed powder mixture of B4C nanopowders (similar to 40 mu m) with coarse Ti-Al powders (similar to 38 mu m) as transient liquid-phase sintering additives was environmentally-friendly prepared by aqueous colloidal processing, optimized by measurements of the zeta potential of dilute suspensions and rheological studies of concentrated suspensions. Second, the powder mixture obtained by freeze-drying was densified by spark-plasma sintering (SPS), identifying the optimal SPS temperature (1850 degrees C) by measurements of density, hardness, and toughness. Third, the dry sliding-wear behaviour of the optimal superhard B4C composite (similar to 31.5 GPa) was investigated by pin-on-disk tests and observations of the worn surface, determining its specific wear rate (similar to 4.4.10(-8) mm(3)/(N.m)) as well as wear mode (two-body abrasion) and mechanism (plastic deformation). And lastly, the wear behaviour of the ultrafine-grained B4C composite was compared with that of a reference fine-grained (similar to 0.7-0.9 mu m) B4C composite, finding that both have the same mode and mechanism of wear but with the former being more resistant than the latter (similar to 2.3.10(7) vs 1.9.10(7) (N.m)/mm(3)). Implications for the fabrication of B4C tribocomponents with greater superior wear resistance are discussed.

Automated summary

An ultrafine-grained B4C composite with superior wear resistance was developed through fabrication, microstructural characterization, and mechanical and tribological testing. The study optimized the preparation process, identified the optimal sintering parameters, investigated the wear behavior, and compared it with a reference fine-grained B4C composite, demonstrating the potential for fabricating B4C tribocomponents with greater superior wear resistance.