Patent ID: 8460482

Claim:
A heat-resistant alloy spring made of a Ni-based alloy material which is a wire material having a wire diameter of not more than 4 mm, said Ni-based alloy material comprising in weight %: not more than 0.1% C; not more than 1.0% Si; not more than 1.50% Mn; 13.0 to 25.0% Cr; 5.5 to 7.0% Mo; 0.5 to 4.0% Ti; 0.1 to 3.0% Al; 12.0% to 18.0% Co; at least one optional element selected from the group consisting of 0.15 to 2.50% W, 0.001 to 0.020% B, 0.01 to 0.3% Zr, 0.30 to 6.00% Nb, and 0.03 to 2.00% Cu; the balance being essentially Ni; and incidental impurities, wherein said Ni-based alloy material has in its crystal structure crystals which have gamma prime phase [Ni 3 (Al, Ti)] or gamma prime phase [Ni 3 (Al, Ti, Nb)] and twin crystals, the gamma prime phase having an average grain diameter (d) of not less than 25 nanometers, and wherein a hardness-diameter ratio (Hv/d) of the average grain diameter (d) (nanometer) and a Vickers hardness Hv measured at a certain depth from a surface of the Ni-based alloy material being 5 to 25 and said certain depth is one-fourth of the wire diameter, and when crystal grains having grain diameters of not less than 10 micrometers are counted in a field of observation view, the percentage Nc/Ns of the total count Ns of the crystal grains and the count Nc of twin crystal grains is not less than 30%.