PURPOSE:To provide a precipitation strengthened Ni alloy having high resistance to stress corrosion cracking in high-temp. water by incorporating C, B and Mn in an adequate ratio range into a specifically composed Ni alloy contg. Cr and Fe and added with Al, Ti and Nb without incorporating Mo therein. CONSTITUTION:This alloy consists of the Ni alloy contg., by weight, 0.010-0.080% C, 0.0001-0.0030% B, 14.0-17.0% Cr, 1.0-10.0% Fe, 0.40-2.00% Al, 2.00-3.00% Ti, 0.50-1.50% Nb and if necessary contg. 0.01-0.10% Mn and consisting of the balance Ni. The alloy has a gamma' phase and Cr23C6 in the austenite phase base and the contents of C and B have the relation within the range enclosed by the straight lines connecting the points A (0.010% C, 0.0030% B), B (0.030%, C, 0.0030% B), C (0.080% C, 0.0020% B), D (0.080% C, 0.0001% B), E (0.010% C, 0.0001% B).
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