Ziqi Jie

Grain Refinement on Microstructure and Mechanical Properties of IN718 Superalloy

The mixed refiner of Co3FeNb2 and CrFeNb ternary intermetallic compounds and melt superheating treatment under the modified thermally-controlled solidification (TCS) process have been designed to achieve grain refinement and further improve mechanical properties of IN718 superalloy. It is found that the refinement effect of addition grain refiners under TCS process is quite superior to that by convention casting (CC) process with refiner, as experiment results show that the grain size is refined from 3340 to 126 μm and greatly reduce the amount of porosity, during the refinement process. In addition, the applied melt treatment can refine grain size from 6420 to 89 μm and greatly reduce the amount of porosity. Meanwhile, after grain refinement, the stress rupture property under 650 °C/620 MPa is significantly improved. Grain refinement mechanisms are also discussed.