A precipitation hardenable, cobalt-nickel base superalloy is disclosed. The is characterized by the following weight percent composition. C about 0.01 to about 0.15 Cr about 6.00 to about 15.00 Ni about 30.00 to about 45.00 W about 3.00 to about 15.00 Ti about 0.50 to about 4.00 Al about 3.00 to about 7.00 Nb up to about 2.50 Ta up to about 6.00 Hf up to about 1.50 Zr up to about 1.50 B up to about 0.20 Mo up to about 2.50 Si up to about 1.50 The balance of the alloy is cobalt and usual impurities. The alloy provides a novel combination of strength and ductility after long-term exposure to elevated operating temperatures as found in gas turbines and jet engines. A fine-grain steel article made from the alloy is also disclosed. The steel article is also characterized by a continuous surface layer of AI 2 O 3 and Cr 2 O 3 that protects the alloy from oxidation at the elevated operating temperatures.