SiC纤维/YSZ复合热障厚涂层韧性及热震性能研究

Toughness and Thermal Shock of Si C Fiber/Yttria-stabilized-zirconia Composite Thick Thermal Barrier Coatings

采用大气等离子喷涂(APS)技术,以Zr O2-8wt%Y2O3(8YSZ)和团聚的P7216(8YSZ和珍珠岩粉)粉末为原料,在基体上制备了厚度大于4 mm的Si C纤维/YSZ(SFY)复合厚热障涂层,通过扫描电子显微镜(SEM)分析了涂层的显微结构,发现SFY涂层具有钢筋混凝土结构,这种结构能够防止因为涂层厚度增加而引起的失效。此外,基于计算机的断层成像技术分析热障涂层孔隙率的变化,考察了SFY涂层和YSZ热障涂层的抗热震性能、断裂韧性以及热导率性能,并探讨了纤维的增韧机制。研究结果表明,SFY涂层具有更高的断裂韧性值和更好的抗热震性能,25℃时SFY涂层的热导率为0.632 W/(m·K),大约是传统YSZ热障涂层热导率的一半。Si C纤维对涂层内部裂纹的偏转和截止作用,防止了裂纹扩散长大,形成网状微裂纹结构,有效提高了涂层的抗热震性能和断裂韧性。

Using ZrO2-8wt%Y2O3 （8YSZ） and agglomerated P7216 （8YSZ and Perlite powder ） powders as raw ma- terials, SiC fiber/YSZ （SFY） composite thick thermal barrier coatings （TBCs, 〉4 turn in thick） were prepared by At- mospheric Plasma Spray （APS） on substrate. The microstructures of columnar coating were analyzed by scanning electron microscope （SEM）. It showed that SFY coatings had a reinforced concrete frame structure, which protected the coatings from failure caused by thickened coatings. Based on the technique of computed tornography, the porosity of TBCs were investigated. And the thermal shock, fracture toughness and thermal conductivity （TC） of both SFY and YSZ coatings were examined and discussed for the SiC fiber toughening mechanism. Test results showed that the SFY coatings had higher fracture toughness and better thermal shock resistance than the YSZ TBCs. At 25 ℃, the TC of SFY coatings was 0.632 W/（m· K）, about 50% reduction of typical APS YSZ TBCs. Data from this study showed that the SiC fiber effectively hindered crack growth and diffusion by crack deflection and crack termina- tion of SFY coating, which was beneficial for growing of the reticular microcrack and improving thermal shock resistance and fracture toughness.