THE APPLICABILITY OF NORTONS CREEP POWER-LAW AND ITS MODIFIED VERSIONTO A SINGLE-CRYSTAL SUPERALLOY TYPE CMSX-2

Creep experiments at 982 degrees C indicate that the Norton creep powe r law and its modified version can be used to describe the creep behav ior, over an extensive amount of deformation, of the nickel-base preci pitation-strengthened single-crystal (SC) superalloy type CMSX-2 by co ntinuously changing the parameters in the equations describing these l aws. The exponent n in Norton's law keeps changing with the amount of total creep deformation of the alloy, reaching a peak value upon rafti ng of the initially cuboidal precipitates. A new empirical exponential relation was observed between the two parameters of the Norton creep power law. This exponential relation indicates that the activation ene rgy for the creep process is linearly proportional to the exponent in Norton law, it changes continuously as the deformation of the SC progr esses and it also peaks during rafting of the precipitates.