Investigation of the residual stress in reaction-bonded SiC under irradiation

The development of reaction-bonded SiC (RB-SiC) for an application in nuclear reactor environments has been suspended for many years because of the possible swelling mismatch between SiC and Si under irradiation. Therefore, we studied the residual stresses in RB-SiC due to the irradiation-induced swelling mismatch and the mismatch between the coefficients of thermal expansion. The maximum irradiation-induced swelling stress for the amorphous state was obtained by irradiation with 2 MeV Au²⁺ ions (1 × 10¹⁶ ions/cm²) at room temperature. Utilizing Raman piezo-spectroscopy, nanoindentation tests and thermal expansion coefficient measurements, we demonstrate that the irradiation-induced swelling stress is remarkably high at low temperatures, whereas the thermal stress becomes the dominant residual stress at medium (415 °C < T < 700 °C) or higher temperatures. By optimizing the residual Si content in the RB-SiC, the thermal stress and the irradiation-induced swelling stress can be adjusted and the initiation of cracks can be prevented.