In situ high-temperature 3D imaging of the damage evolution in a SiC nuclear fuel cladding material

•Fracture processes in a coated SiC composite nuclear cladding material were found different at room temperature and 1200 °C.•At both temperatures, cracking initiated in the outer monolithic SiC coating.•The stress and strain when first coating crack occurred are much higher at 1200 °C than room temperature.•Typical crack toughening mechanisms occurred simultaneously in underlying composites upon load drops at both temperatures.