Dependence of Accelerated Creep Rate at 580 °C and Room Temperature Yield Stress for Two Creep Resistant Steels

Abstract

Two creep resistant steels, P91 and X20, were tempered for 17520 h at 650 8C or 8760 h at 750 8C to study the growth and redistribution of carbide precipitates in martensite. On specimens annealed for a different time, yield stress at room temperature and accelerated creep rate at 580 8C were determined. With increasing yield stress in the range from 350 to 650 MPa the accelerated creep rate decreased continuously by about 2 orders of magnitude from 8Á10 À7 s À1 to 5Á10 À9 s À1 . For equal yield stress, the creep rate was slightly lower for the steel P91 than for the steel X20.