Al2O3-ZrO2 eutectic ceramic via ultrasonic-assisted laser engineered net shaping

Abstract Al2O3-ZrO2 eutectic ceramic structures of thin wall and cylinder with average eutectic spacing 60–70 nm were prepared by ultrasonic-assisted laser engineered net shaping (LENS). Effect of ultrasonic power on micro-topography was investigated. X-ray diffractometer analysis and scanning electron microscopy observation were carried out for sample phase composition and micro-topography respectively. The friction and wear properties were tested by microcomputer control universal friction and wear tester. Thermal stability and microhardness were measured by synchronous thermal analyzer and vivtorinox hardness tester respectively, and surface fracture toughness was calculated by indentation crack length. The results show that with the increase of ultrasonic power from 20 to 110 W, micro-topography is cellular eutectic, cellular coexisting with dendritic eutectic, dendritic eutectic, dendritic coexisting with cellular eutectic in turn. Eutectic spacing is 60.29 nm while ultrasonic power is 120 W, grain boundary and colony organization are eliminated completely. When the ultrasonic power changes in 20–160 W, the eutectic spacing shows a tendency to decrease first and then increase. Surface fracture toughness increases to 7.67 ± 0.2 MPa m1/2. The reasons for improvement of fracture toughness were analyzed from the aspects of refined eutectic spacing and residual compressive stress. Friction coefficient is small and has no big fluctuation. Wear mechanism exhibits intergranular brittle fracture and exfoliation wear.