镍基高温合金铸件的晶粒组织控制──铸造工艺参数的影响

GRAIN STRUCTURECONTROL OF NICKEL-BASE SUPERALLOYSIN CASTINGPROCESSES: EFFECTOFFOUNDRY VARIABLES

以ＩＮ７３８ＬＣ合金为例，研究了镍基高温合金在各种铸造工艺条件下的晶粒组织。结果表明，降低合金液均匀化处理温度可以明显细化冷凝后基体的晶粒。在浇注温度、铸型预热温度以及合金液均匀化处理温度等铸造工艺参数中，后者对晶粒尺寸的影响大于前两者。

Grain structures of nickel-base superalloy IN 738LC are invesitated under various casting conditions. It is found that grain size of y matrix and dimension of MC carbides reduce obviously by lowering the temperature of melt homogeneous treatment.The mechanism of grain refinement can be the existence of a number of unmeIted MC particles that serve as the substrata of nonspontaneous nucleation of y matrix during freezing.By comparing meIt pouring tempera-ture,mold preheating temperature with melt homogeneous treatment temperature,it can be con cluded that the last one plays a more predominant role on the grain structures than the first two。Therefore,one of the effective methods of refining grain structures is via controlling the melt homogeneous temperature.