A Ni-base alloy which has excellent resistance to permanent set at high temperature
and which can be produced at low cost, a heat-resistant spring made of the Ni-base
alloy, and a process for producing the spring. The Ni-base alloy of the present
invention consists of 0.01 to 0.15 mass % of C, 2.0 mass % or less of Si, 2.5 mass
% or less of Mn, 12 to 25 mass % of Cr, 5.0 mass % or less of Mo and/or 5.0 mass
% or less of W on condition that Mo+W/2 does not exceed 5.0 mass % or less, 1.5
to 3.5 mass % of Ti, 0.7 to 2.5 mass % of Al, 20 mass % or less of Fe, and the
balance of Ni and unavoidable impurities. The ratio of Ti/Al in terms of atomic
percentage ranges from 0.6 to 1.5 and the total content of Ti and Al ranges from
4.0 to 8.5 atomic %.
