Investigation on Nickel base superalloy steam turbine bolts fractured at high temperatures, a case history

摘要

Ni-base superalloys have been often used as material for bolts of the steam turbine valves and of the steam admission areas of the turbine casings, thanks to their high-temperature resistance properties. In order to withstand high creep and fatigue loading these alloys are strengthened by γ' and/or γ" precipitates.