Oxidation Behavior of Alumina Fiber Reinforced SiCO Composites for a Co‐Firing Process on Steel Pipes

Abstract

In order to increase the operating temperature of power plants up to 700 °C and to reduce the revision intervals at the current temperatures (550 °C), the temperature and pressure‐induced load of a hot steam pipe can be decreased by a ceramic matrix composite (CMC) jacket, that consist of alumina fibers (Nextel 610) within a SiCO matrix. Due to the creep resistance of the CMC jacket, the lifetime of the steel tube is significantly enhanced [Spatz et al., J. Eur. Ceram. Soc. 2018, 38, 2954]. Within this work, the influence of oxidation of this specifically developed CMC jacket material on the mechanical properties and microstructure is examined at 550 °C up to 500 h. Polymer infiltration and pyrolysis (PIP) is applied in order to fabricate unidirectional fiber reinforced oxide CMCs at 750 °C in N2. Open porosities below 15%, shear strengths up to 18 MPa, and tensile strength up to 230 MPa are obtained after 500 h at 550 °C. In order to analyze the effect of oxidation and thermal treatment, the amount and the distribution of porosity, which cause significantly changes within the microstructure, and the mechanical properties of the oxide composites are studied and discussed.