Co-based superalloys depend on carbide precipitation and solid solution strengthening for mechanical properties. While these strengthening mechanisms are inferior to gamma prime (γ') precipitation strengthening, cobalt has a higher melting point than nickel and has superior hot corrosion resistance and thermal fatigue. As a result, carbide-strengthened Co-based superalloys are used in lower stress, higher temperature applications such as stationary vanes in gas turbines.
Cos γ/γ microstructure was rediscovered and published in 2006 by Sato et al. That γ phase was Co(Al, W). Mo, Ti, Nb, V, and Ta partition to the γ phase, while Fe, Mn, and Cr partition to the matrix γ.
The next family of Co-based superalloys was discovered in 2015 by Makineni et al. This family has a similar γ/γ microstructure, but is W-free and has a γ phase of Co(Al,Mo,Nb). Since W is heavy, its elimination makes Co-based alloys increasingly viable in turbines for aircraft, where low density is especially valued.
The most recently discovered family of superalloys was computationally predicted by Nyshadham et al. in 2017, and demonstrated by Reyes Tirado et al. in 2018. This γ' phase is W free and has the composition Co(Nb,V) and Co(Ta,V).