Cobalt-base super alloys (e.g. UNS R30155 (Grade 661) and R30816 (Grade 671)) have superior strength to the nickel base alloys above 1800°F (980°C).

The refractory metal alloys (including tantalum, tungsten, niobium, and molybdenum) are not typically used in high temperature applications, except as alloying elements.  They are commercially available, but are often used in environmentally protected applications.  Minor additions of niobium and molybdenum to stainless steels and nickel-base alloys typically enhance high temperature properties.