Ni-based superalloys have found widespread use in high-temperature, low stress applications. Fe-based superalloys are generally not used at high temperatures as the γ’-phase is not stable in the Fe matrix, but are sometimes used at moderately high temperatures, as iron is significantly cheaper than nickel. Co-based γ’ structure was found in 2006, allowing the development of Co-based superalloys, which are superior to Ni-based superalloys in corrosion resistance. However, in the base (Co-W-Al) system, γ’ is only stable below 900 °C, and Co-based superalloys tend to be weaker than their Ni counterparts.