Effect of melting state on the thermal shock resistance and thermal conductivity of APS ZrO2–7.5wt.% Y2O3 coatings

• Published in: Surface & coatings technology Vol. 270; pp. 132 - 138
• Main Authors: Song, Xuemei, Liu, Ziwei, Suhonen, Tomi, Varis, Tommi, Huang, Liping, Zheng, Xuebin, Zeng, Yi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 25.05.2015
• Subjects: Air plasma spraying; Coatings; Columnar grains; Grains; Heat transfer; Shock resistance; Thermal conductivity; Thermal shock resistance; YSZ coatings; Yttria stabilized zirconia; Yttrium oxide; Zirconium dioxide; Columnar grains; Thermal conductivity; YSZ coatings; Air plasma spraying; Thermal shock resistance
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2015.03.011

The microstructures of two types of ZrO2–7.5wt.% Y2O3 (YSZ) coatings fabricated by air plasma spraying (APS) but containing different amounts of columnar grains were investigated through scanning electron microscopy and electron backscatter diffraction analysis. Differences in the formation mechanisms of columnar and equiaxed grains were characterized using particles collected in a water container, from which it was found that these mechanisms are closely related to the melted state of the in-flight particles. Furthermore, it was found that the higher the columnar grain concentration of an as-sprayed coating, the higher its thermal shock resistance. This means that it is possible to improve the thermal shock resistance of APS YSZ coatings simply by introducing more columnar grains, as this increases their thermal conductivity. Using this knowledge, YSZ coatings with good thermal shock resistance and a thermal conductivity of 0.81W·(m·K)−1 at 1100°C were successfully prepared. •YSZ coatings with columnar grains in different amounts were fabricated by APS.•Formation mechanisms of microstructures were explained by water-quenched particles.•How to improve the thermal properties of YSZ coatings were investigated.•YSZ coatings with good thermal shock resistance were obtained by APS.•Effects of phase composition on thermal conductivity of YSZ coatings were studied.