Abstract: 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.

摘要： 本文以50kg真空感应熔炼的镍基合金Ni-24Fe-14Cr-8Mo为实验材料,通过采取不同温度、不同时间的高温扩散热处理,结合光学显微镜、扫描电子显微镜、电子探针分析仪以及金相照片图像分析的手段,围绕温度和时间对合金组织中Laves相回溶以及元素偏析的影响开展研究。结果表明,合金枝晶间岛状低熔点金属间化合物Laves相的析出造成严重的元素偏析,Laves相初熔温度在1180～1200℃;在1180℃ 7～100 h扩散热处理时,Laves相体积分数随处理时间呈V_f=11.557 8_exp（-0.143 2 t）的指数规律减小,在1180℃保温40 h以内Laves相不能完全回溶,而保温76 h以上则Laves相可以完全回溶,保温100 h可以进一步消除元素偏析。Ni-24Fe-14Cr-8Mo合金的高温扩散热处理温度不应高于Laves相初熔温度,采取1180℃保温100 h有效地减少Laves相比例以及元素偏析。