莫来石/氧化铝预应力涂层增强氧化铝的弯曲强度和抗热震性能

在陶瓷表面引入含压应力的涂层是一种有效的增强技术。本研究将氧化铝和石英粉混合浆料涂覆在预烧后的氧化铝坯体上, 无压共烧原位合成了热膨胀系数较低的莫来石-氧化铝涂层。利用降温过程中涂层内形成的残余压应力实现了氧化铝陶瓷的预应力强化。结果表明：随着涂层中石英掺量增加, 预应力氧化铝的强度出现先增大后减小的趋势; 当涂层中掺入石英的质量分数为15%时, 预应力增强效果最好, 涂层与基体界面结合紧密, 预应力氧化铝陶瓷的弯曲强度达到(549.44±27.2) MPa, 比普通氧化铝的强度提高了37.19%; 当涂层中掺入石英的质量分数增大到15%以上, 由于烧结收缩不匹配反而引起强度下降; 这种预应力增强效果会随着温度升高逐渐减弱, 当测试温度达到并超过1000 ℃时, 预应力氧化铝和普通氧化铝会具有大致相等的抗弯强度。由于表层压应力的存在, 预应力氧化铝还展现出更好的抗热震性能和损伤耐受性。

Enhanced Flexural Strength and Thermal Shock Resistance of Alumina Ceramics by Mullite/Alumina Pre-stressed Coating

It is an effective strengthened technique to introduce a coating containing compressive stress on the surface of ceramic. In this work, the mixed slurry of alumina and quartz powder was coated on the pre-sintered alumina body, then the mullite-alumina coating with lower thermal expansion coefficient was synthesized in-situ after pressureless co-sintering. The pre-stressed strengthening of alumina was achieved by the residual compressive stress formed in the coating during the cooling process. The results indicate that, with the increase of the doping content of quartz in the coating, the flexural strength of pre-stressed alumina increases firstly and then decreases. The flexural strength of specimen realizes the highest value when the doping mass fraction of quartz is 15%, and the interface between the coating and the substrate bonds tightly. Under this condition, the flexural strength of the pre-stressed alumina ceramic is (549.44±27.2) MPa, which is 37.19% higher than that of the common alumina. When the doping mass fraction of quartz is higher than 15%, the flexural strength decreases due to the shrinkage stress mismatch in the sintering process. The effect of prestress enhancement weakens gradually with the increase of temperature. As the testing temperature reaches and exceeds 1000 ℃, pre-stressed alumina and common alumina possess approximately equal flexural strength. Pre-stressed alumina also exhibits better thermal shock resistance and damage tolerance due to the compressive stress formed in the coating