Microstructure and modelling of the deformation behaviour of CoCr22Ni22W14 in hot-tensile- and creep tests

The present study describes the application of hot tension experiments in order to predict the creep and tensile behaviour of the highly loaded superalloy CoCr22Ni22W14. The results of mechanical tests and transmission electron microscopy (TEM) investigations have been used as input data in a model which describes the high temperature plastic deformation. A common log ɛ - log σ plot of tensile and creep data shows a systematic shift of about 10% towards higher stresses in the case of tensile loading. In creep tests the dislocation densities reach their steady-state values at the points of minimal strain rates, whereas in tensile tests the dislocation densities increase at any given time until the tensile strength is reached at significantly higher strains. Under the condition of equal true stresses subgrain formation is more pronounced after tensile than after creep deformation. By including the experimentally determined dislocation densities, the constitutive model yields qualitatively correct predictions of the creep and tensile behaviour.