CRACKING OF 08X18H10T STEEL AND XH35BT ALLOY USED IN STEAM-GENERATORSIN NUCLEAR-POWER-PLANTS

Cracking of the collector flanges (08X18H10T steel) and studs (XH35BT alloy) of steam generators used in nuclear power plants is investigate d. From the analysis of the damaged flange material and laboratory tes ts, it was concluded that the 08X18H10T steel, lubricated with molybde num disulfide and exposed to a high-temperature (300 degrees C) alkali ne solution, experiences transgranular cracking even in an unstressed state. The decomposition of the additive causes the extensive hydrogen ation of the metal and its hydrogen embrittlement under conditions of the active-to-passive transition of the steel surface and sulfur adsor ption. Transgranular microcracks on the thread surface of the studs or iginate by a similar mechanism, while their flat part, which is out of contact with the 08X18H10T steel, undergoes intergranular alkaline cr acking.