Abstract
The effect of partial Fe substitution for Ni on microstructure, lattice misfit, oxidation, creep, and yield strength are investigated for six W-free cobalt-based superalloys with compositions Co-(30-x)Ni-xFe-yCr-5Al–3V–2Ti-1.5Nb-1.5Ta-0.08B (at.%), with three levels of Fe (x = 12, 14, or 18, replacing Ni) and two levels of Cr (y = 4 or 8, replacing Co). Alloys with 12 and 14% Fe exhibit mostly γ/γʹ microstructures after aging up to 1000 h at 850 °C, while those with 18% Fe display additional intermetallic phases. All alloys show positive lattice misfit from 0.56 to 0.34%, with Fe substitutions reducing lattice misfit by ∼0.02% per 1 at.% Fe. Increasing Fe from 12 to 18% reduces oxidation rates for both levels of Cr. Substitution of Ni by Fe also increases solvus temperature but reduces creep resistance at 850 °C as well as yield strength below 800 °C. By contrast, increasing Cr from 4 to 8 at.% improves both oxidation and creep resistance at 850 °C.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
