Thermo-mechanical fatigue of Ni-base superalloys

Important results from the project

The goal this project is that using mechanical testing study how Haynes 282 behaves under isothermal and thermo-mechanical loading, and to link this to the deformation and failure mechanisms of the material. The mechanical testing showed that the material exhibited large anisotropy with low ductility in the transverse direction. The investigation revealed that type and distribution of carbides had great influence on the mechanical properties. The anisotropy can be explained with the string of carbides arising from the manufacturing of the material.

Expected long term effects

Within the project an expertise has been built in mechanical testing at high temperature. At the department are now skills so that high-temperature can be performed by existing standards. Extensive investigations of the microstructure of Haynes 282 have been performed. The reasons for the anisotropy of the material are the type and distribution of carbides, which in turn depends on the process parameters in the production of the base material, process parameters in the forging and how the material is heat treated. The results from the project have adverse carbide structures identified

Approach and implementation

In this project, various types of mechanical tests on Haynes 282 performed. Isothermal low cycle fatigue tests have been carried out in the temperature range from 300C to 730C, and the total strain range at 0.6, 1.0 and 2.0%. Thermo-mechanical tests have been carried out with temperature cycles from 300C to 730C, and strain range in phase and out of phase at 0.6, 1.0 and 2.0%. Also fractographic studies and characterization by optical microscope and scanning electron microscope was performed.