Stress Corrosion Cracking Behavior of SiC/SiC_f Composite Cladding Tube in High-Temperature and High-Pressure Water

The stress corrosion cracking (SCC) test of SiC/SiC_f composite cladding tube in high temperature and high pressure water was carried out by three-point bending loading method, which simulated the chemical conditions of PWR primary water. The SCC resistance of the material was analyzed by corrosion morphology. The results show that under the action of three-point bending loading and high temperature and high pressure water environment, the outer coating of the composite cladding tube was oxidized and corroded, and crack propagation and spalling occurred in some areas. The spalling of the coating further aggravated the corrosion and dissolution of the outer coating, resulting in premature failure of the outer coating and exposure of the SiC fiber layer. Under the coupling effect of stress and water chemical environment, corrosion dissolution and crack propagation appeared in the interlayer of SiC fiber. The crack propagation on the surface of the SiC fiber layer had no obvious orientation, and the continuous generation of cross cracks eventually led to the fracture and overall failure of the fiber layer. Stress concentration was easy to occur at the pore defects on the coating surface, which becomed the location of crack initiation. It is necessary to optimize the coating preparation process.