改进单晶高温合金性能的途径

WAYS TO IMPROVE THE MECHANICAL PROPERTIES OF A NICKEL BASE SINGLE CRYSTAL SUPERALLOY

采用籽晶法在自制的高温高梯度ＬＭＣ定向凝固设备上制取了以平面、胞状、粗枝以及细枝界面形态凝固的ＮＡＳＡＩＲ１００单晶。研究了其铸态以及经１２８０℃、１３００℃和１３２０℃×４ｈＡ．Ｃ．处理的组织和性能。结果表明，快速的抽拉速率和尽可能高的固溶温度显著改善单晶高温合金的性能，在相同的抽拉速率下，高温度梯度显著降低显微疏松含量，缩小树枝晶间距，并且能够得到细小的、形状较规则的γ′相。

he NASAIR100 single crystal solidified with the planar,cellular,coarse dendritic and fine dendritic solid liquid interfaces are obtained using‘ seed’ technique in the LMC directional solidification device with higher temperatures and higher thermal gradients made by ourselves.The microstructure and mechanical properties are studied under as cast and 1280℃,1300℃and1320℃×4h A. C. heat treated conditions.The resultS show that the microsegregation getS more and more severe andthe temperature at which the as-cast γ′and γ/γ′ eutectic can be throughly soluted becomes higher and higher as the solid liquid interface shape is turned from the planar into the cellular, then the coarse dendritic and finally the fine dendritic, Compared to the low thennal gradients in industrial production condition,the high thermal gradient can considerably improve the casting quality,and thus enhanee the high tempcrature mechanical properties of the single crystals.A high withdrawal rate and a soluting temperature as high as possible can further improve the mechanical properties.