PRECIPITATION OF A PI-PHASE IN AUSTENITIC STEELS DURING CREEP

In microstructural investigations of X 2 CrNiN 18 10 and X 15 CrNiSi 2 0 12 steels, precipitation of pi-phase was identified in the specimen regions severely damaged by cavitation processes during creep rupture test in air. In both steels the precipitation of pi-phase was dependen t on the penetration of air into the body of the specimens along inter linked grain boundary cavities. Our findings prove that under certain conditions, pi-phase particles can precipitate in plain CrNi austeniti c steels with higher silicon contents even if the steels are not alloy ed with nitrogen.