Effects of carbon addition on the microstructure and mechanical properties of Ir85Nb15 two-phase refractory superalloy

To provide information relevant to Ir-base two-phase alloys for future ultra-high-temperature applications, effects of carbon addition on the structure development and mechanical properties of a two-phase Ir85Nb15 alloy were investigated. The results show that carbide formation is not necessary for stabilising the grains in the two-phase Ir85Nb15 alloy at temperatures up to 1800 °C. At temperatures up to 1200 °C, the yield strength of the carbon-doped Ir85Nb15 alloys was higher than that of the carbon-free alloy. The carbon addition to the Ir85Nb15 alloy changed the fracture mode from intergranular to transgranular cleavage.