Enhanced thermal shock response of Al ₂ O ₃ –graphite composites through a layered architectural design

The use of ceramics such as alumina in moving components often requires the addition of low friction materials such as graphite. A new strategy for improving toughness, strength, and thermal-shock resistance of Al ₂ O ₃ –graphite self-lubricating composites was proposed in this study. Alumina layers embedded between Al ₂ O ₃ –graphite layers were fabricated and tested after thermal shock conditions ranging between 500 °C and 800 °C maximum temperature. Retained strength and apparent fracture toughness after the tests were compared to room temperature values. Results show that compressive residual stresses generated in the outer Al ₂ O ₃ –graphite layers during cooling down from sintering improve the failure resistance of the materials. The introduction of heat-resistant particles (Al ₂ O ₃ particles) into graphite layers combined with a layered architecture can greatly decrease the oxidation degradation of the materials below 500 °C. In addition, the retained strength and toughness in the layered architectures after thermal shock between 550 °C and 800 °C remains constant, thus indicating that the new-developed Al ₂ O ₃ /Al ₂ O ₃ –graphite laminated composites may be reliable candidates for self–lubricating applications also for elevated temperatures.