Abstract
The effects of charging temperature and time on the embrittlement of cathodically hydrogen charged specimens were investigated by tensile test and scanning-electron microscopic studies on Alloy 600 single crystals with ‹100› tensile axis. Many cracks on the specimen surface were observed along {100} traces. Crack depths don't exceed several ten microns and correspond to the thickness of hydride formed during the charging. Fracture strength and elongation after the charging decreased with the increases in charging temperature and time. The crystallographic plane of fractured surface always consists of {100} plane. There was a relation, h∝t1/2, between the depth of brittle layer (h) and charging time (t). The diffusion coefficient (Dl) of hydrogen atoms in the grain is about one tenth of that along grain boundary. The activation energy for the diffusion obtained from the temperature dependence of Dl was estimated to be 14.2kcal/mol.
