Three-dimensional Continuous Structure Research Articles

Improving the tribological properties of ZrO2(Y2O3)-graphite composites at high temperature through three-dimensional continuous structure

ZrO2(Y2O3)-graphite composites with a three-dimensional (3D) continuous structure were prepared by using a core-shell design of graphite and ZrO2(Y2O3). The effect of structure on the friction-reducing and anti-wear mechanisms from room temperature to 700 °C was investigated. During high-temperature friction, abrasive wear and brittle fracture are the main wear mechanisms for ZrO2(Y2O3)-graphite composites with homogeneous composition. For the composites with 3D structure, the continuous ZrO2 matrix with high load-carrying capacity and the formation of a dense friction layer with self-lubricating and thermal oxidation resistance improve the tribological properties significantly, reducing the coefficient of friction by about 10% and the wear rate by nearly two orders of magnitude when coupled with GH4169 alloys at 600 °C.

Fabrication and high-temperature tribological behaviors of Al2O3/Cr2O3 composites with three-dimensional continuous structure

A new strategy for improving high-temperature compressive strength and tribological properties of Al2O3/Cr2O3 composites was proposed in this study. The three-dimensional (3D) continuous Al2O3 ceramic matrix containing Cr2O3 particles was fabricated, and the influencing mechanisms of compositions and structures on the anti-wear and friction-reducing performance of composites at high temperature were revealed. Results show that the enrichment degree of Cr2O3 in the composites can be significantly improved based on the 3D continuous structure design compared with Al2O3/Cr2O3 composite containing uniform compositions. Under friction conditions, the Cr2O3 phase with large enrichment degree can preferentially contact with the micro-asperities on the friction pair surface under the action of grain refinement at high temperature, so that the softened Cr2O3 is easy to be sheared and dragged to the worn surfaces of the frictioncouples to form the friction film and transfer film. Meanwhile, under the favorable effect of the high load-carrying capacity of continuous Al2O3 matrix, Al2O3/Cr2O3 composites show excellent tribological properties at high temperature. The friction coefficient and wear rate of Al2O3/Cr2O3 composites with 3D continuous structure sliding against Al2O3 pin can be reduced to 0.35 and 2.2 × 10-6 mm3·N-1m−1 at 800 °C, and it still presents excellent friction-reducing and anti-wear properties at 1000 °C.