Steels: Microstructure and properties

Abstract

The steel Grade E911 has been developed from Grade P91, in the frame of the European 501 COST Progranune. to increase the creep properties at 600C through the control of vanadium, nitrogen and the addition of tungsten. The comparison between Grade P91 and E911 in terms of mechanical and creep properties, long time exposure, both in term of mechanical and microstructure evolution, are presented. The Grade 911 shows a performance better than Grade 91: its extrapolated stress to obtain a rupture at 600C in 105 hours is now about 110 MPa instead of 95 MPa for the Grade 91. Microstructure stability of both the steels was investigated by isothermal ageing tests for up to 10000 hours at 600 and 650C and some mechanical behaviour are compared. The results show that the tensile properties and ductility are maintained.