Abstract: The Si₃N₄/h-BN self-lubricating composites were prepared by hot-press sintering technique, and the effects of different shapes of h-BN on the phase structure, microstructure, mechanical properties and high-temperature tribological properties of Si₃N₄/h-BN self-lubricating composites were investigated. The results show that compared with the flaky h-BN, the spherical h-BN promotes the formation of three-dimensional continuous structure of Si₃N₄ matrix, which increases its flexural strength (369 ± 15.6 MPa) and fracture toughness (5.3 ± 0.78 MPa·m^1/2) by about 8%. And during high temperature friction, abrasive wear and brittle fracture are considered as the main wear mechanisms of Si₃N₄/h-BN self-lubricating composites. When the three-dimensional structured composites (prepared from spherical h-BN) are friction with Si₃N₄ at 800 ℃, the formation of a continuous Si₃N₄ matrix with high load-bearing capacity as well as a dense and continuous friction layer with self-lubricating and highly thermally stable reduces the coefficient of friction by about 23%, and reduces the wear rate by nearly an order of magnitude compared to homogeneous structural composites (prepared from flaky h-BN).

Key words: Si₃N₄/h-BN self-lubricating composite, three-dimensional continuous structure, high temperature, anti-friction and anti-wear