Microstructure and Nanomechanical Property of Plasma-Sprayed Nanostructured Yb2SiO5 Environmental Barrier Coatings

In this study, nanostructured Yb2SiO5 coatings were prepared by atmospheric plasma spraying (APS) using nanostructured Yb2SiO5 feedstocks. Conventional Yb2SiO5 coatings were selected for comparison. The microstructure and nanomechanical property of the nanostructured and conventional Yb2SiO5 coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and nano-indentation. Results indicate that the surface of the nanostructured Yb2SiO5 coatings is uniform and denser than the conventional Yb2SiO5 coatings. In addition, Weibull distribution analysis shows that the molten state of the nanostructured Yb2SiO5 coatings present a mono-modal distribution, whereas the conventional Yb2SiO5 coatings show a bi-modal distribution, i.e. molten and unmelted zones. The nanostructured Yb2SiO5 coatings have a higher elastic modulus than the conventional Yb2SiO5 coatings (167.37077 ± 16.88070 GPa versus 153.72856 ± 19.69907 GPa), reflecting their high density.

Thermal Shock Behavior and Particle Erosion Resistance of Toughened GZ Coatings Prepared by Atmospheric Plasma Spraying

Gadolinium zirconate with excellent high-temperature phase stability and sintering resistance has become a very promising candidate material for a new generation of thermal barrier coatings (TBCs). However, the low fracture toughness of gadolinium zirconate greatly limits its application. In this study, gadolinium zirconate (GZ) and two kinds of toughened gadolinium zirconate (GZ/YSZ prepared by mixed powder of Gd2Zr2O7 and YSZ and GSZC prepared by (Gd0.925Sc0.075)2(Zr0.7Ce0.3)2O7 powder) double-layered TBCs were prepared by atmospheric plasma spraying (APS). The fracture toughness of the GZ/YSZ coating and GSZC coating were 9 times and 3.5 times that of GZ coating, respectively. The results of thermal shock test showed that the three TBCs exhibit different failure mechanisms. During the thermal shock test, cracking occurred at the interfaces between the YSZ layer and the BC or GZ/YSZ layer, while GSZC TBC failed due to premature cracking inside the GSZC layer. The particle erosion rate of the GZ, GZ/YSZ, and GZSC coatings were 1.81, 0.48, and 1.01 mg/g, respectively, indicating that the erosion resistance of coatings is related to their fracture toughness. Furthermore, the superior erosion resistance of the GZ/YSZ and GSZC coatings can be attributed to the conversion of crack propagation path during the erosion test.