A comparison of creep models for nickel base alloys for advanced energy systems

Creep behavior was reviewed for five nickel base alloys of interest to the ultrasupercritical steam boiler and Gen-IV nuclear reactor materials programs. The behavior was evaluated, qualitatively, on the basis of creep models commonly employed to represent creep of solid-solution, wrought superalloys. These models ranged from the simple Norton creep law to rather sophisticated unified equations and continuum damage mechanics (CDM) models. In view of the heat-to-heat variability of the alloys, it was found that for representation of strains of interest to design applications, the Norton power law was suitable. Alloys that exhibited little or no primary or secondary creep were better modeled by means of the CDM approach.