Creep, fatigue, and environmental response of Alloy 800H tested at 900 degrees C

Creep and creep rupture studies have been carried out at 900;A direct current potential drop technique was utilized to monitor in situ creep strain. A high speed data acquisition system was employed to collect and transform the direct current potential drop data. This methodology was found to provide accurate measurements of creep strain even in notched specimens.;A finite difference method was developed to perform second derivative analysis of the creep curves. This technique showed that it is possible to quantitatively identify the end points of the various creep stages as well as to identify crack initiation and crack advance events.;High resolution electron metallography was performed on the creep and creep rupture specimens, and a finite element analysis of smooth and notched specimens was used, in conjunction with this microstructural data, to aid in the interpretation of the smooth and notched specimen failures.