Assessment of the solid particle erosion resistance, microstructure and failure mechanism of calcia, magnesia, and yttria-stabilized zirconia thermal barrier coatings

Abstract

In thermal barrier coatings (TBCs), different stabilizing compositions are preferred to increase the strength and optimize the thermal expansion coefficient of zirconia-based ceramic top coatings. In this study, TBC systems containing ZrO2-CaO (CSZ), ZrO2-MgO (MSZ) and ZrO2-Y2O3 (YSZ) were produced by atmospheric plasma spraying (APS) method and solid particle erosion (SPE) tests were performed at 30 degrees, 60 degrees and 90 degrees impact angles in accordance with ASTM G76-95 standard. In tests using alumina powders, it was determined that erosion behavior is closely related to microstructural properties and mechanical strength. At low angles (30 degrees-60 degrees), the sliding of particles along the surface led to stress accumulation at lamellar boundaries, microcracks and especially in interconnected pores, which increased the wear. In addition, low hardness and high surface roughness reinforced this effect. In contrast, YSZ coatings exhibited the lowest wear rate at 90 degrees impact angle due to their higher hardness, low interconnected pore content and uniform surface morphology. The results revealed that microstructural integrity and mechanical properties play a decisive role in the erosion resistance of TBC systems.