Testing Advanced SiC Fiber Tows at Elevated Temperature in Silicic Acid-Saturated Steam
Investigating stressed oxidation and scale crystallization kinetics of advanced SiC fibers at elevated temperature in steam is a challenging yet essential undertaking for the assessment of the effects of oxidation on mechanical properties of SiC-SiC ceramic matrix composites (CMCs). Moisture in the oxidizing environment is known to change oxidation rates, reduce scale viscosity and lower temperatures for scale crystallization. In order to study these phenomena, a facility for testing SiC fiber tows in creep at elevated temperatures in air, in steam and in steam saturated with silicic acid was developed. The newly constructed test facility was validated through creep testing of Hi-Nicalon™-S fibers at 800°C in steam saturated with silicic acid. Testing in saturated steam resulted in formation of a uniform oxide scale. Details of the test facility design, development and experimental validation are presented.