Hot Corrosion, Oxidation and Their Effects on the Tensile Strength of SiC Fiber in Alkaline Melts

Abstract

An experimental study on the behavior of hot corrosion and oxidation of SiC fiber (Hi-Nicalon^TM) coated with the film of varied alkaline melts was investigated at 1000°C. The hot corrosion and oxidation of SiC fiber were characterized by specific mass loss. The tensile properties on the fibers before and after hot corrosion were evaluated by room temperature single filament test technique. The specific mass loss and strength retention after hot corrosion indicated that the corrosion effect of Hi-Nicalon^TM fiber in sodium carbonate was more severe than in sodium sulfate. The corrosion effects of Na₂SO₄ could be enhanced by addition of small amount of Na₂CO₃/NaNO₃. Scanning electron microscopy (SEM) and X-ray diffractometer (XRD) revealed that the degradation of SiC fiber in corrosive and oxidative environment was mainly related to the interaction between the alkaline melts and silica scale. Furthermore, the excess carbon in Hi-Nicalon^TM fiber must enhance the hot corrosion and oxidation leading to the degradation in microstructure and mechanical properties.