INCONEL718超合金鍛造材の極低温疲労特性(非鉄材料,<特集>ギガサイクル疲労)

概要

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High-cycle fatigue properties at 4K, 77K and 293K were investigated in forged-Inconel 718 nickel-based superalloy with a mean gamma(γ) grain size of 25μm. In the present material, plate-like delta phases precpitated at γ grain boundaries and niobium enriched-MC type carbides precipitated coarsely. The 0.2% proof stress and the ultimate tensile strength of this alloy increased with decreasing temperature, without decreasing elongation or reduction of area. Fatigue strength in longer-life region did not increase in response to increments in tensile strength, since fatigue cracks initiated internally irrespective of the test temperatures. Fatigue cracks formed crack initiation sites consisting of facet-like structures. These facet-like structures mainly corresponded to coarse carbides at higher stress amplitude and crystallographic facets formed through transgranular initiation and growth of micro cracks at lower stress amplitude.
社団法人日本機械学会の論文
2004-08-25