NI계 초내열 합금 CMSX-4의 TMF거동 및 조직변화

Abstract

Cyclic deformation behavior of a single crystal Ni-based superalloy, CMSX-4 has been investigated during Thermo-mechanical fatigue (TMF). TMF cycle is defined as a condition where uniform temperature and strain fields over the specimen gage section are simultaneously varied and independently controlled. TMF of structural materials have been topics of intense research interest among materials scientists and engineers for over fifty years, and are subjects that continue to receive considerable attention. TMF testing plays an increasingly important role in the design, the reliability assessment and the life-cycle management of safety critical components used, for instance, for power generation, in the process industry and in aeronautical and automotive applications, with a view to increasing the fuel efficiency, safety and service intervals, while reducing production and material costs. In this study, the CMSX-4 is Ni-based superalloy which will be used in gas turbine blades. Induction heating coil system utilized to operate at high temperature state. The TMF tests were conducted over a temperature range of 400-950℃.A simple triangular fully-reversed strain cycle with a mechanical strain range of ±0.3%∼0.6% was imposed out of phase(OP) with the temperature cycle; i.e. the minimum temperature corresponds to the maximum tensile strain. It was observed that as mechanical strain are increased more and more slip band deformation were increased as well. This result as mechanical strain are increased more and more TMF life were decreased as well. It appears that large amount of slip band may cause a significant life reduction of TMF compare to LCF life.