Thermal evolution behavior of carbides and 纬鈥?precipitates in FGH96 superalloy powder

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• 作者：Lin Zhang^a ; ^{zhanglincsu@163.com} ; Hengsan Liu^a ; ^{lhsj63@sohu.com} ; Xinbo He^a ; ^{xb_he@163.com} ; Rafi-ud-din^a ; ^{rafiuddi@gmail.com} ; Xuanhui Qu^a ; ^{quxh@ustb.edu.cn} ; Mingli Qin^a ; ^{mlqin75@hotmail.com} ; Zhou Li^b ; ^{zhouli621@126.com} ; Guoqing Zhang^b ; ^{g.zhang@126.com}
• 关键词：Nickel based superalloys ; Powder metallurgy ; Precipitation ; Carbides ; Microstructure
• 刊名：Materials Characterization
• 出版年：2012
• 期刊代码：57_10445803
• 类别：ms
• 出版时间：May, 2012
• 卷：67
• 期：Complete
• 页码：52-64
• 文件大小：3684 K

摘要

The characteristics of rapidly solidified FGH96 superalloy powder and the thermal evolution behavior of carbides and 纬鈥?precipitates within powder particles were investigated. It was observed that the reduction of powder size and the increase of cooling rate had transformed the solidification morphologies of atomized powder from dendrite in major to cellular structure. The secondary dendritic spacing was measured to be 1.02-2.55 渭m and the corresponding cooling rates were estimated to be in the range of 1.4 脳 10⁴-4.7 脳 10⁵ K路s^鈭?#xA0;1. An increase in the annealing temperature had rendered the phase transformation of carbides evolving from non-equilibrium MC鈥?carbides to intermediate transition stage of M₂₃C₆ carbides, and finally to thermodynamically stable MC carbides. The superfine 纬鈥?precipitates were formed at the dendritic boundaries of rapidly solidified superalloy powder. The coalescence, growth, and homogenization of 纬' precipitates occurred with increasing annealing temperature. With decreasing cooling rate from 650 掳C路K^鈭?#xA0;1 to 5 掳C路K^鈭?#xA0;1, the morphological development of 纬鈥?precipitates had been shown to proceed from spheroidal to cuboidal and finally to solid state dendrites. Meanwhile, a shift had been observed from dendritic morphology to recrystallized structure between 900 掳C and 1050 掳C. Moreover, accelerated evolution of carbides and 纬' precipitates had been facilitated by the formation of new grain boundaries which provide fast diffusion path for atomic elements.