A cobalt-base superalloy chemical composition is disclosed which includes, in % by weight: 25-28 W; 3-8 Al; 0.5-6 Ta; 0-3 Mo; 0.01-0.2 C; 0.01-0.1 Hf; 0.001 -0.05 B; 0.01-0.1 Si; and remainder Co and unavoidable impurities. This superalloy can be strengthened by γ′ dispersions and further dispersion mechanisms. Exemplary compositions can provide good oxidation properties and improved strength values at high temperatures.