Improvement of Fracture Toughness and Low-Cycle Fatigue Life for INCONEL718 Welded Joint in the LE-7 Rocket Engine Main Injector.

Hasegawa, Keiichi; Ando, Kiyoshi; Kitade, Shouji; Sakamoto, Mitsumasa; Fukushima, Yo; Okita, Koichi

doi:10.1299/kikaia.61.1707

Cited by 4 publications

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“…Additionally, this alloy has been used for structural materials in aerospace industry, since this alloy has good weldability and good tensile properties in strength and ductility at cryogenic temperatures. 1,2) In recent years, the mechanical properties of structural materials used for Japanese-built launch vehicles have been studied with the aim of increasing their reliability. 3,4) The mechanical properties at cryogenic temperatures in IN718 need to be investigated since this alloy is used for, for example, liquid oxygen turbo-pumps and there is few data on high-cycle fatigue properties at cryogenic temperatures.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2004

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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 () grain size of 25 mm. In the present material, plate-like delta phase precipitated at 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 10 7 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.

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Section: Introductionmentioning

confidence: 99%