STRUCTURE UNIFORMITY AND CREEP BEHAVIOR OF MODIFIED NICKEL BASE ALLOY NIMOCR

摘要

The thermomechanical (TM) processing of NiMoCr solid solution nickel base superalloy is a process to influence considerably the grain characteristics of the wrought structures. The initial as-cast ingot structure break down by hot working usually does not provide uniform recrystallized grain structure. In order to modify the structure heterogeneity in roughly forged ingot the conventional two steps hot rolling was conducted. Post deformation annealing was applied expecting further contribution in modification of primary recrystallized microstructure. The uniformity of alloy microstructure increased as higher straining of slab was introduced. Nevertheless the deformation condition were applied the bimodal grain structure was typical applying the specific TM experimental schedules. The creep behaviour of differently modified alloy structure after various hot working conditions and the annealing process were then investigated for considered testing condition. The results of creep tests showed that creep characteristics such as strain rate and lifetime are greatly dependent on resulting microstructure.