Effect of Grain Size on High Temperature Low-cycle Fatigue Properties of Inconel 617

Abstract

The effect of grain size on the high temperature low-cycle fatigue behavior and other material strength properties of Inconel 617 was studied at 1273 K in air. The strain controlled low-cycle fatigue tests were conducted with a symmetrical (FF type) and an asymmetrical (SF type) strain wave forms. The latter wave form was used for the evaluation of creep-fatigue interaction.
The main results obtained in this study are as follows:
1) The tensile strength slightly increased with the increase of the grain diameter. On the other hand, the tensile ductility remarkabley decreased with the increase of the grain diameter.
2) The creep rupture life remarkabley increased with the increase of the grain diameter, especially at the lower stress levels. The effect of grain size on creep ductility has not detailed.
3) The low-cycle fatigue life remarkably decreased with the increase of the grain diameter, especially at the lower strain ranges.
4) The creep-fatigue life was less sensitive to the grain diameter than the fatigue life, because the grain size effects on creep and on fatigue were contrary. It is seemed that the creep-fatigue life is determined by the proportion of the creep and fatigue contribution.
5) The fatigue and creep-fatigue test results have good relations with the tensile and creep ductilities at the test temperature.