Berlin 2005 – scientific programme

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M: Metallphysik

M 32: Poster TU B (Symposium Tomographic Methods in Materials Research M-32.32-55)

M 32.43: Poster

Monday, March 7, 2005, 14:30–16:30, Poster TU B

High resolution synchrotron tomography on Nickelbase superalloys — •Thomas Link¹ und Alexander Epishin² — ¹Dr. T. Link, TU Berlin BH18, Ernst-Reuter-Platz 1, 10587 Berlin — ²Dr. A. Epishin, BAM-Berlin, Unter den Eichen 87, 12205 Berlin

Single crystals of Nickel base superalloys contain micro pores, resulting from solidification, heat treatment and creep deformation. The investigated specimens have rod shape. They are grown by directional solidification, resulting in a dendritic structure along the rod axis. SEM images of cross sections through the rods gave an indication, that the pores are arranged preferably in the interdendritic region. Because the pore volume fraction is quite low, about 0.3 percent, this is difficult to be seen in a 2D image. Therefore tomography was applied. The pores under interest are quite small, around 5 microns, and the density of the superalloys high. This restricted the thickness of the specimens to about 0.5mm. They were investigated at the ID19 beamline, ESRF, Grenoble under 50 keV. The main points of interest were: Porosity in undeformed superalloys of the 3 generation (SRR99, CMSX-4, CMSX-10). Development of porosity in CMSX-4 during creep. Influence of the creep stress on the creep porosity. We could show, that porosity is most pronounced in the newest superalloy. Porosity increases during creep. With rising creep stress the creep pores form also in the primary and secondary dendrite arms.