Effect of Mo concentration on creep properties of a single crystal nickel-base superalloy

The effect of Mo concentration on creep properties of a single crystal nickel-base superalloy has been studied at 1010 °C and 800 °C by using three kinds of alloys with 1%, 2% and 4% of Mo (wt.). The creep properties of alloys were measured and microstructure evolution was analyzed. The results showed that after heat treatment, all the three alloys were composed of γ and γ′ phase without TCP phase precipitation. The increase of Mo concentration from 1 wt.% to 2 wt.% pronouncedly enhanced the creep properties. Compared with 1 wt.% Mo content, 2 wt.% Mo addition can generate denser γ/γ′ interfacial dislocation networks during high temperature creep test, thus lower minimum creep rate. At medium temperature creep condition, Mo addition enhanced creep properties by decreasing the stacking fault energy. When the Mo content reached to 4%, the over-saturation of Mo content in γ phase led to the formation of μ phase precipitation which degraded the creep properties at both high and medium temperature creep conditions.