Improving the thermal shock resistance and fracture toughness of synthesized La2Ce2O7 thermal barrier coatings through formation of La2Ce2O7/YSZ composite coating via air plasma spraying

Abstract

Due to the substantial brittleness of the thermal sprayed coatings, fracture mechanic can effectively illustrate the applicability of such surface layers. Lanthanum-cerium oxide (LC) coatings usually show poor thermal sock behavior even at low temperatures, mainly induced by their low fracture toughness and decreased coefficient of thermal expansion. At the first step, this study deals with the solid state synthesis of LC. At the next step, the synthesized LC and YSZ used to apply composite coatings (monolithic LC, 75 wt% LC-25 wt% YSZ, 50 wt% LC-50 wt% YSZ, 25 wt% LC-75 wt% YSZ and monolithic YSZ) through thermal spray method. The fracture toughness and thermal shock resistance of the formed coatings were then investigated. X-ray diffraction spectroscopy, energy dispersive spectroscopy and field emission scanning electron microscopy were used to study the phase analysis, chemical composition and morphological investigations of the coatings, respectively. Results indicated that higher fraction of YSZ can lead to enhanced fracture toughness due to higher energy relieving rate. The best thermal shock resistance outcome was also achieved in LC-50 wt% YSZ composite coating, as the coating tolerated 350 thermal cycles.