Effects of fine porosity on the fatigue behavior of a powder metallurgy superalloy |
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Authors: | R V Miner R L Dreshfield |
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Affiliation: | (1) NASA-Lewis Research Center, 21000 Brookpark Road, 44135 Cleveland, OH |
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Abstract: | Hot-isostatically-pressed powder-metallurgy Astroloy was obtained which contained 1.4 pct, fine porosity at the grain boundaries
produced by argon entering the powder container during pressing. The pores averaged about 2μ,m diam and 20 μ m spacing. This
material was tested at 650 °C in fatigue, creep-fatigue, tension, and stress-rupture and the results compared with previous
data on sound Astroloy. The pores influenced fatigue crack initiation and produced a more intergranular mode of propagation.
However, fatigue life was not drastically reduced. A large 25 μm pore in one specimen resulting from a hollow particle did
reduce life by 60 pct, however. Fatigue behavior of the porous material showed typical correlation with tensile behavior.
The plastic strain range-life relation was reduced proportionately with the reduction in tensile ductility, but the elastic
strain range-life relation was little changed reflecting the small reduction in strength divided by modulus for the porous
material. |
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