Comparison of the Mechanical Behavior and Evaluation of Different Damage Mechanisms in an Equiaxed and a Single Crystal Superalloys Subjected to Creep LCF and TMF

Abstract

Hot gas path components in a gas turbine engine for power generation have to withstand to critical conditions in terms of temperature and load distribution. The requirement of higher flexibility of gas turbine engines drives the OEM producer to increase their knowledge of materials behaviour when creep and fatigue coexist. This paper tries to summarise and compare the microstructural damage evolution in two superalloys applied in Ansaldo gas turbine engine components with a different solidification process, Rene 80 and PWA 1483 SX. The samples from an intensive campaign of mechanical characterisation were used to study damage features after creep, LCF and TMF tests. They have been analysed through standard metallography and advanced characterisation techniques, like EBSD and In-Beam detector in a FEG-SEM. In depth microstructural investigations enabled characterization of damage evolution as a function of testing conditions and highlighted the differences that exist between equiaxed and single crystal alloys. For both the alloys creep-fatigue interaction happens also in presence of compressive hold time LCF and TMF cycles.