In situ Formation of Oxidation Resistant Refractory Coatings on SiC-Reinforced ZrB2 Ultra High Temperature Ceramics

In situ oxidation resistant and solid refractory coatings have been generated on 20 vol% SiC-reinforced ZrB2 ultra high temperature ceramics containing 10 wt% rare earth (RE) additives such as LaB6, La2O3, and Gd2O3 fabricated by spark plasma sintering. Oxidation for 1 h at 1600 degrees C in static air led to formation of a dense layer (up to 250 mu m thick) of ZrO2 and RE-zirconates on the composite systems underneath which were intermediate layers (50-100 mu m) containing heterogeneous crystalline oxides such as La2Zr2O7 and amorphous silicate phases. The benefits of predominating solid oxidation products over having substantial volumes of liquid present in aerospace leading edge applications are discussed.