Abstract :
In order to investigate the formation, distribution, growth behavior and volume fraction of
porosity at high temperatures in ferritic Oxide Dispersion Strengthened (ODS) superalloys
MA 956, ODM 751 and PM 2000 were exposed at 1100 and 1200◦C in air and in 2% oxygen
containing nitrogen atmospheres for up to 8760 h. All samples exhibited small amounts of
porosity (% <0.1) in the as-received condition. During the early stages of exposure (up to
10 h) pores were generally located close to the surface of the samples. Later they were
found in the central region of the samples and the volume fraction of porosity and the
mean pore size increased. After exposure for 240–1000 h, mainly depending on sample
thickness, the size and volume fraction of porosity reached a maximum value and then
decreased. SEM and EDS analysis results showed that some pores contained small
amounts of Ti, Al and Y rich particles which were distributed over the internal surface of
pores. It was noted that when the volume fraction of porosity and the size of pores began to
decrease the pores had filled with the matrix material. A relation was established between
the production environment of the materials and the growth behavior of the pores.
C 2005 Springer Science + Business Media, Inc.
