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.
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.
