The effect of silicon on the microstructure and segregation of directionally solidified IN738 superalloy

Abstract

The effect of silicon on the microstructure and solidification segregation of directionally solidified IN738 nickel-based superalloy was studied. Directional solidification at various solidification rates and partial directional solidification plus rapid quenching were applied. Metallographic analysis and an electron microprobe were mainly used to observe and measure the microstructure and elemental segregation of the alloy, respectively. It was found that silicon affected the morphology of the liquid-solid interface of the alloy during solidification and gave the alloy a tendency to form well-developed dendrites. The addition of silicon enlarged the solidus-liquidus temperature interval, and the solidification rate also greatly influenced the interval. The interval increased with increasing solidification rate. Silicon promoted the precipitation of the gamma/gamma' eutectic, and also affected its precipitation temperature. Silicon segregated mainly in interdendritic regions, and promoted the segregation of other elements. All of the effects of silicon on the alloy related to the solidification rate.