In this paper

the influence of high temperature diffusion heat treatment on Laves phase and elements segregation in 50 kg vacuum induction melted Ni-24Fe-14Cr-8Mo nickel base alloy is studied. The alloy is heat-treated at different temperatures for different times

and the microstructure and element distribution are investigated through Optical Microscope (OM)

Scanning Electron Microscope (SEM)

Electron Probe Micro-Analyzer (EPMA) and Metallographic Processing (MP). Results indicate that island-shaped Laves phase obviously precipitates in the interdendritic area led to a serious elements segregation. The incipient temperature of Laves phase is at 1180 ~ 1200 ℃. When the alloy is soaked at 1180 ℃ for

7 ~ 100 h

the volume fraction of Laves phase kept decreases with diffusion treatment time in an exponential pattern with V

f

= 11.557 8

exp

( -0.1432 t) ； Laves phase could not be totally dissolved in less than 40 h but almost disappeared after 76 h at 1180℃；elements segregation could be further improved after 100 h high temperature diffusion heat treated at 1180℃.It could be concluded that for Ni-24Fe-14Cr-8Mo alloy the high diffusion heat treatment temperature should not be higher than incipient temperature Laves phase

and a treatment at 1 180 °C for 100 h could effectively reduce Laves phase fraction and elements segregation.