CARBON ADDITIONS AND GRAIN DEFECT FORMATION IN HIGH REFRACTORY NICKEL-BASE SINGLE CRYSTAL SUPERALLOYS
CARBON ADDITIONS AND GRAIN DEFECT FORMATION IN HIGH REFRACTORY NICKEL-BASE SINGLE CRYSTAL SUPERALLOYS
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DOI：
10.7449/2000/superalloys_2000_201_210
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
S. Tin;T. Pollock;W. T. King
中科院分区：
文献类型：
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作者：
S. Tin;T. Pollock;W. T. King
采用两个半析因试验设计，在12种不同的“第二代”镍基单晶高温合金中研究了合金添加剂对合金凝固特性的影响。实验合金，与C，W，Re，Ta，Al和Hf的组成变化，凝固为圆柱形棒在一个大的集群模具。在恒定的加工条件下，名义上类似的实验合金含有0.125重量%的添加剂，C表现出降低的趋势，发展晶粒缺陷，如雀斑链。碳的添加导致在形成三个富Ta的MC碳化物的形态沉淀的合金的液相线温度附近。有意的碳添加也影响了组成元素的偏析行为。使用Scheil型分析测量的分配系数的比较表明，W和Ta的偏析较少发生在实验单晶合金中含有碳。初步观察表明，碳/碳化物的相互作用可能会改变高密度耐火合金元素的偏析行为，并影响糊状区的性质的方式，降低热溶质对流的驱动力。
Using two half fractional factorial experimental designs, the effect of alloying additions on the solidification characteristics of single crystal Ni-base superalloys has been studied in twelve distinct “2nd generation” type alloys. The experimental alloys, with compositional variations of C, W, Re, Ta, Al and Hf, were solidified as cylindrical bars in a large cluster mold. Under constant processing conditions, nominally similar experimental alloys containing additions of 0.125 wt.% C exhibited a decreased tendency to develop grain defects, such as freckle chains. The carbon additions resulted in the formation of three Ta-rich MC carbide morphologies which precipitate near the liquidus temperature of the alloy. Intentional carbon additions also affected the segregation behavior of the constituent elements. Comparison of distribution coefficients measured using a Scheil-type analyses revealed that less segregation of Wand Ta occurred in the experimental single crystal alloys containing carbon. Preliminary observations suggest that carbon/carbide interactions may potentially change the segregation behavior of high density refractory alloying elements and affect the properties of the mushy zone in a manner which decreases the driving force for thermosolutal convection.