The Interpretation of Experimental Observation Data for the Development of Mechanisms based Creep Damage Constitutive Equations for High Chromium Steel

It is very important to design a safe factor or estimating the remain lifetime for electric power plant components of steam pipes which mostly manufacture by high chromium steels and work at high temperature and low stress level. The author will develop the mechanisms based on creep damage constitutive equations for high chromium steel under lows stress in initial stage: (1) Creep cavities mostly formed attaching with the precipitation of Laves phase or on grain boundary for high chromium steel under low stress. The Laves phase should play an active role in the nucleation of creep cavities and suggest to explore the function between cavity nucleation and the evolution of Laves phase; (2) The dominant cavity nucleation mechanism is adapted to high chromium steels under low stress level; (3) Brittle intergranluar model is appropriate for high chromium steels at high temperature under low stress level; (4) High density number of cavity of crept test high chromium steel at high temperature under low stress could be as fracture criterion. Keywords-high chromium steel; cavitation; Constitutive equations; low stress