Thermal evolution behavior of carbides and γ′ precipitates in FGH96 superalloy powder
Thermal evolution behavior of carbides and γ′ precipitates in FGH96 superalloy powder
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DOI：
10.1016/j.matchar.2012.02.014
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发表时间：
2012-05
影响因子：
4.7
通讯作者：
Lin Zhang;Hengsan Liu;Xin-Bo He;Rafi-ud-din;X. Qu;Mingli Qin;Zhou Li;Guo-qing Zhang
中科院分区：
文献类型：
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作者：
Lin Zhang;Hengsan Liu;Xin-Bo He;Rafi-ud-din;X. Qu;Mingli Qin;Zhou Li;Guo-qing Zhang
研究了快速凝固FGH 96高温合金粉末的特性及粉末颗粒中碳化物和γ′相的热演化行为。结果表明，随着粉末粒度的减小和冷却速度的提高，雾化粉末的凝固形态由枝晶为主转变为胞状结构。测得二次枝晶间距为1.02-2.55μm，相应的冷却速率估计为1.4×104-4.7× 105 K·s-1。随着退火温度的升高，碳化物的相变由非平衡MC′碳化物向M23 C6碳化物的中间过渡阶段转变，最终转变为热稳定MC碳化物。在快速凝固高温合金粉末枝晶界面处形成了超细γ′相。随着退火温度的升高，γ'相逐渐聚结、长大和均匀化。随着冷却速率从650°C·K− 1降低到5°C·K−1，γ′相的形态发展由球状到立方状，最后转变为固态枝晶。同时，在900°C和1050°C之间观察到从枝晶形态到再结晶结构的转变。此外，新晶界的形成为原子元素的快速扩散提供了通道，加速了碳化物和γ'相的演化。
The characteristics of rapidly solidified FGH96 superalloy powder and the thermal evolution behavior of carbides and γ′ 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 1.02–2.55μm and the corresponding cooling rates were estimated to be in the range of 1.4×104–4.7×105K·s−1. An increase in the annealing temperature had rendered the phase transformation of carbides evolving from non-equilibrium MC′ carbides to intermediate transition stage of M23C6carbides, and finally to thermodynamically stable MC carbides. The superfine γ′ precipitates were formed at the dendritic boundaries of rapidly solidified superalloy powder. The coalescence, growth, and homogenization of γ' precipitates occurred with increasing annealing temperature. With decreasing cooling rate from 650°C·K−1to 5°C·K−1, the morphological development of γ′ 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°C and 1050°C. Moreover, accelerated evolution of carbides and γ' precipitates had been facilitated by the formation of new grain boundaries which provide fast diffusion path for atomic elements.