Directional solidification experiments were carried out at 0.5- 150 ㎛/s in the Co-base superalloy ECY 768. As increasing solidification rate, the dendrite length increased and it reached the maximum at 150 ㎛/s, where the tip temperature is close t...
Directional solidification experiments were carried out at 0.5- 150 ㎛/s in the Co-base superalloy ECY 768. As increasing solidification rate, the dendrite length increased and it reached the maximum at 150 ㎛/s, where the tip temperature is close to the liquidus. The liquidus and eutectic temperatures could be estimated by comparing the dendrite lengths and the temperature gradients at the solid/liquid interface and those were estimated as 1424.6oC and 1343oC respectively. Between the dendrites just below final freezing temperature, MC carbide and M23C6 carbide were found. It was confirmed that the script or blocky shape was Ta or W-rich MC carbide, and the lamellar shape was Cr-rich carbide. Solid/liquid interface morphology clearly showed that the Cr-rich eutectic carbide formed just after the script type MC carbide.