Zirconia based pyrochlore thermal barrier coatings

Abstract

Improvements in thermal barrier coatings (TBCs) technology, further than what is already in service to enable adequate protection to metallic components from higher (>1100°C) operating temperatures requires newer developments in materials. Many research activities have been undertaken by scientists to seek alternatives after discovering the threshold of Yttria-stabilized zirconia (YSZ) TBCs on standard aero-space materials at elevated temperatures. To increase the thermal performance of gas turbine engines, alternate TBC materials with better sintering resistance and lower thermal conductivity are required. One of the promising candidates for the TBCs is Pyrochlore-type rare earth zirconium oxides (Re2Zr2O7, Re = rare earth). Re2Zr2O7 TBCs have higher phase stability, lower thermal conductivity, lower sintering rate, no phase transformation, and lower coefficient of thermal expansion at elevated temperatures when compared with YSZ. In this work, plasma spray powders of Lanthanum Zirconate (La2Zr2O7) and Lanthanum Ceria Zirconate (La2 (Zr0.7Ce0.3)2O7) were synthesized by the solid-state reaction method with the goal to develop pyrochlore oxide-based coatings with desired properties at high temperatures (>1200°C), better than the YSZ TBCs: Currently the most popular choice for TBCs. These TBCs are expected to increase gas turbine efficiencies while protecting the underlying metallic substrate at high operation temperatures. The evaluation of the synthesised TBCs has been carrying out by studying their performances at 1200°C. Results of evaluation for phase composition by employing X-Ray Diffractometry (XRD), microstructure via Scanning electron Microscope (SEM) and chemical composition via Energy Dispersive spectroscopy (EDS) also have been included.