Properties and microstructure of machinable Al2O3/LaPO4 ceramic composites

Layer structured LaPO4 was added to Al2O3 ceramic matrix to improve the machinability of the composites. Densification, hardness and microstructures of the Al2O3/LaPO4 ceramic composites have been studied at various sintering temperatures (1300, 1400, 1500, 1600 °C) and different LaPO4 contents (pure Al2O3, 10 wt.% LaPO4, 20 wt.% LaPO4, 30 wt.% LaPO4, 40 wt.% LaPO4, pure LaPO4). X-ray diffraction analysis showed that only Al2O3 and LaPO4 phases exist in the Al2O3/LaPO4 composites with different LaPO4 content even sintered up to 1600 °C. Bulk density, hardness and microstructures of the Al2O3/LaPO4 composites are largely dependent on the LaPO4 content and sintering temperature. Due to the layered structure of LaPO4 and the weak interface between the Al2O3 and LaPO4 phase, the 40 wt.% Al2O3/LaPO4 composite can be easily machined using cemented carbide drills instead of conventionally diamond tools.