To provide a Ni-based austenitic superalloy with a low thermal expansion, having a coefficient of thermal expansion equal to that of a ferrite-based 12Cr steel, and high-temperature strength and corrosion/oxidation resistance equal to that of an austenite-based heat resistant alloy.
This super alloy includes carbon 0.15 mass% or less, silicon 1 mass% or less, manganese 1 mass% or less, chromium 5-20 mass%, molybdenum 17-26 mass%, aluminum 0.1-2.0 mass%, titanium 0.1-2.0 mass%, iron 10 mass% or less, boron 0.02 mass% or less, zirconium 0.2 mass% or less, tungsten, rhenium, and the balance substantially nickel, while the sum of aluminum and titanium content is 1-5.5 atom.%, satisfying the expression: 17≤Mo+(W+ Re)/2≤27, where Mo indicates a molybdenum content by mass%, W indicates a tungsten content by mass%, and Re indicates a rhenium content by mass%. The super alloy, further has a structure, in which a γ'-phase consisting of intermetallic compounds, and a A2B-phase consisting of intermetallic compounds, form composite precipitates.
KADOYA YOSHIKUNI
UMAGOE RYUTARO
NODA TOSHIHARU
ISOBE SUSUMU
OKABE MICHIO
KAWAI HISATAKA
DAIDO STEEL CO LTD