Effect of Withdrawal Rates on Microstructure and Creep Strength of a Single Crystal Superalloy Processed by LMC

Chengbao Liu1), Jian Shen1), Jian Zhang2) and Langhong Lou1) 1) Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China 2) National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China

摘 要：A nickel base single crystal （SC） superalloy was directionally solidified using liquid metal cooling （LMC） process at various withdrawal rates. The microstructure was refined as increasing the withdrawal rate from 3 to 12 mm/min. However, higher withdrawal rate of 15 mm/min induced the formation of stray grains. Size and volume fraction of the eutectics were found to decrease with the increasing in withdrawal rate. After solution heat treatment at 1250℃, un-dissolved eutectic was observed in specimens. High temperature creep rupture life was observed to be very sensitive to the fraction of these remaining eutectics. Creep rupture tests at 1000℃/235 MPa showed that refined microstructure and low fraction of the remaining eutectic lead to significant improvement of the rupture life.

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