High-Cycle Fatigue Properties at Cryogenic Temperatures in INCONEL 718 Nickel-based Superalloy

Accession number;04A0177597
Title;High-Cycle Fatigue Properties at Cryogenic Temperatures in INCONEL 718 Nickel-based Superalloy
Author;ONO Y(National Inst. For Materials Sci. (mits/nims), Tsukuba, Jpn)   YURI T(National Inst. For Materials Sci. (mits/nims), Tsukuba, Jpn)   SUMIYOSHI H(National Inst. For Materials Sci. (mits/nims), Tsukuba, Jpn)   TAKEUCHI E(National Inst. For Materials Sci. (mits/nims), Tsukuba, Jpn)   MATSUOKA S(National Inst. For Materials Sci. (mits/nims), Tsukuba, Jpn)   OGATA T(National Inst. For Materials Sci. (mits/nims), Tsukuba, Jpn)   
Journal Title;Mater Trans
Journal Code:G0668A
ISSN:1345-9678
VOL.45;NO.2;PAGE.342-345(2004)
Figure&Table&Reference;FIG.7, TBL.2, REF.15
Pub. Country;Japan
Language;English
Abstract;High-cycle fatigue properties at 4 K, 77 K and 293 K were investigated in forged-INCONEL 718 nickel-based superalloy with a mean gamma (.GAMMA.) grain size of 25 .MU.m. In the present material, plate-like delta phase precipitated at .GAMMA. grain boundaries and niobium (Nb)-enriched MC type carbides precipitated coarsely throughout the specimens. The 0.2% proof stress and the ultimate tensile strength of this alloy increased with decreasing temperature, without decreasing elongation or reduction of area. High-cycle fatigue strengths also increased with decreasing temperature although the fatigue limit at each temperature didn't appear even around 107 cycles. Fatigue cracks initiated near the specimen surface and formed faceted structures around crack initiation sites. Fatigue cracks predominantly initiated from coarse Nb-enriched carbides and faceted structures mainly corresponded to these carbides. In lower stress amplitude tests, however, facets were formed through transgranular crack initiation and growth. These kinds of distinctive crack initiation behavior seem to lower the high-cycle fatigue strength below room temperature in the present material. (author abst.)
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