Effect of the Addition of La2O3 on the Properties of ZrO2-Al2O3 Ceramic Composites for Coatings in Aerospace Turbines

Abstract

Ceramic matrix composites have attracted the interest of turbine manufacturers for use in coating hot sections because of their higher capacity to withstand high temperatures and because they have a lower requirement for air cooling. One of the most commonly used ceramic coatings is zirconia-yttria. However, its main disadvantage is the inherent fragility of ceramics, which limits the use of these materials in mechanical structures and industrial applications. Ceramics are generally reinforced with the incorporation of additives to reduce their brittleness and increase their mechanical strength and toughness. It is known that La2O3 which are potential source for stabilization of zirconia composites. In this context, ZrO2-Al2O3-La2O3 based ceramic matrix composites were developed for deposition of a thermal barrier coating on the substrate of exhaust nozzles of aerospace turbines varying the content of La2O3 by 5, 7 and 10 wt%. The composites were produced by a thermomechanical process and sintered at 1385 °C. The properties of these composites were studied by X-ray diffraction, relative density, scanning electron microscopy, and Vickers microhardness tests. The results indicate that the composite with 10% La2O3 has great potential for use as ceramic coatings of turbine exhaust nozzles in the aerospace industry.