等离子喷涂氧化钇稳定氧化锆涂层的分形特征与断裂韧性

采用超音速等离子喷涂和普通大气等离子喷涂制备了微米级氧化钇稳定氧化锆（yttria-stabilized zirconia，YSZ）基热障涂层，使用SprayWatch-2i系统测试喷涂过程中粒子飞行速度及表面温度，通过扫描电镜和图像分析技术表征涂层微观结构，利用压痕法测试了断裂韧性和弹性模量，采用基于分形思想的面积-周长幂率定量表征两种工艺条件下孔隙不规则形态，并研究了分形维数对涂层断裂韧性的影响。结果表明:超音速等离子喷涂和普通大气等离子喷涂YSZ涂层孔隙都具有分形特性；超音速等离子喷涂YSZ涂层分形维数是普通等离子喷涂涂层的1.12倍，孔隙结构更复杂，涂层断裂韧性更高。

Fractal character and fracture toughness of plasma sprayed yttria-stabilized zirconia coatings

Yttria-stabilized zirconia(YSZ)-based thermal barrier coatings(TBCs)in micron size were deposited by supersonic atmospheric plasma spraying(SAPS)and conventional atmospheric plasma spraying(APS).During the spraying,a commercially available online diagnostic system(SprayWatch-2i)was used to monitor the velocity and surface temperature of the in-flight particles for each operating condition.The microstructures of the as-sprayed coatings in two spraying conditions were characterized by the scanning electron microscopy and the image analysis technique.The fracture toughness and elastic modulus were measured by the indentation method.The power law of area-perimeter which originated from the fractal theory was employed to quantitatively characterize the irregular morphology of the pores in two spraying conditions.The relationship of fractal dimension and fracture toughness was also investigated.The results show that,the fractal dimension can characterize the irregular morphology of pores.The coatings deposited by SAPS and APS show the good fractal character.The fractal dimension of the coatings deposited by SAPS is 1.12 times than that of the coatings deposited by APS,showing the more complex pore structure and the higher fracture toughness.