Effect of Y2O3 doping content on phase composition, mechanical properties and cavitation erosion performance of ZrO2 ceramics

Y2O3 stabilized ZrO2 (YSZ) is considered to be promising in resisting force-heat coupling damage caused by cavitation erosion (CE). However, the impact of doping Y2O3 on the microstructure and properties of ZrO2 is extremely complex, and there is still a lack of understanding about it, let alone the mechanism of these factors on the CE performance. In light of this, the present study investigated the effects of Y2O3 doping content (3 mol%, 7 mol% and 17 mol%) on the phase composition, grain size, microstructure, density, mechanical properties and CE performance of YSZ, and deeply analyzed the CE mechanism. The results indicated that the Y3+ entering the zirconia lattice effectively stabilized the high-temperature phases (t, t′ and c) and suppressed the formation of mphase. With the increase of Y3+ concentration, the content of t continuously decreased while that of c continuously increased, so that only t + t′ phases were contained in the 3YSZ and only t′+c phases were contained in the 17YSZ. Meanwhile, the grain sizes and pores were constantly increasing, which obviously deteriorated the hardness, toughness and CE resistance. The t→m transformation under the action of cavitation load effectively absorbed impact energy and suppressed the propagation of fatigue cracks, thereby significantly delaying the fatigue spallation of materials. The 3YSZ with the densest microstructure, the best mechanical properties, the smallest grain size and the highest content of t-phase exhibited the best CE resistance. However, the continuous accumulation of m-phase at the grain edge, especially the amorphous structure formed by hydrolysis promoted by cavitation heat, provided a preferential channel for the propagation of fatigue cracks, and thus ultimately led to the exfoliation of the grains.