含Hf镍基粉末高温合金快速凝固粉末颗粒特性

采用扫描电镜、透射电镜及其附带的能谱仪和碳复型萃取技术等多种手段研究了不同Hf含量的FGH96合金粉末颗粒显微组织、枝晶间合金元素偏析和析出相.发现Hf含量可以改变粉末颗粒内部树枝晶、胞状长大晶和微晶凝固组织的比例,粉末的快速凝固组织形态主要取决于冷却速率和固液界面前沿温度梯度与长大速度的比值.不同Hf含量的FGH96合金粉末颗粒中,Nb、Ti、Zr和Al均富集于枝晶间,Co、Cr、W和Ni均富集于枝晶轴.当Hf质量分数为0.3%时,Ti、Nb、Zr、Hf等强碳化物形成元素的枝晶偏析程度最小.在快速凝固粉末颗粒中,Hf对氧含量比碳含量更敏感,优先形成更稳定的氧化物HfO₂. 

Characteristics of rapidly solidified powder particles in Hf-modified nickel-based P/M superalloys

The effects of Hf content on the microstructure, dendrite microsegregation and precipitated phase of FGH96 superalloy powders were investigated by scanning electron microscopy, transmission electron microscopy with energy-dispersive spectrometry, and carbon extraction method. It is found that Hf content can change the proportion of dendrite, cellular and microcrystal structures. The microstructures of the superalloy powders mainly depend on cooling rate and the ratio of thermal gradient to solid/liquid interface velocity. Nb, Ti, Zr and Al elements enrich between the dendrite arms, but Co, Cr, W and Ni elements enrich in the dendrite axis for all FGH96 superalloy powders with different Hf contents. The dendrite microsegregations of Ti, Nb, Zr and Hf elements are the least when the mass fraction of Hf is 0.3%. Hf is more sensitive to the oxygen content than the carbon of the rapidly solidified powder particles, and forms the stable oxide of HfO₂ firstly.