SwRK-VERSUCHE UND RISSEINLEITUNGSUNTERSUCHUNGEN AM NEUENTWICKELTEN DUPLEXSTAHL X 3 CrMnNiMoN 25 6 4 IM VERGLEICH ZUM BEKANNTEN FERRITISCH-AUSTENITISCHEN STAHL X 2 CrNiMoN 22 5.

The majority of low pressure steam turbine damages are caused by corrosion fatigue. This kind of damage occurs primarily in the Wilson-zone of steam turbine machines. In spite of careful feed water washing there is still a build-up of damaging chloride-containing water impurities on the turbine blades. Recent investigations of duplex stainless-steels, especially the steel X 3 CrMnNiMoN 25 6 4 (A905; austenite/ferrite equals 50/50) show both a good corrosion behavior and a sufficient strength of this type of steel. In the present investigations the dependence on the corrosion fatigue limit on the pH-value, chloride concentration, temperature and the behavior of corrosion cracking (crack initiation) is evaluated.