MICROSTRUCTURE AND MODELING OF THE DEFORMATION-BEHAVIOR OF COCR22NI22W14 IN HOT-TENSILE-TEST 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 loa ded superalloy CoCr22Ni22W14. The results of mechanical tests and tran smission electron microscopy (TEM) investigations have been used as in put data in a model which describes the high temperature plastic defor mation. A common log epsilon - log sigma plot of tensile and creep dat a shows a systematic shift of about 10% towards higher stresses in the case of tensile loading. In creep tests the dislocation densities rea ch their steady-state values al the points of minimal strain rates, wh ereas in tensile tests the dislocation densities increase at any given time until the tensile strength is reached al significantly higher st rains. Under the condition of equal true stresses subgrain formation i s more pronounced after tensile than after creep deformation. By inclu ding the experimentally determined dislocation densities, the constitu tive model yields qualitatively correct predictions of the creep and t ensile behaviour. (C) 1997 Elsevier Science S.A.