增压涡轮用镍基高温合金的凝固特性和热裂倾向性

摘要

The solidification characteristics and the hot tearing susceptibility were investigated on two Ni-based superalloys for turbocharger turbine wheel, K418 and K419. The segregation behaviors of the alloying elements and the precipitation phases were also studied. The results show that the solidification behavior of K419 alloy is complicated when compared with K418 due to the interdendritic segregation of many kinds of strong interdendritic partitioning elements in the remaining liquid at the final stage of solidification. The segregation of multiple elements in interdendritic liquid results in an extremely low solidus in K419. A long residual liquid stage is found during the solidification of K419, giving rise to reduced cohesion strength of dendrites and increased sensitivity to hot tearing. A hot tearing susceptibility coefficient (HTS) criterion is proposed based on a hot tearing sensitive model. The HTS value of K419 alloy is larger than that of K418 alloy.%研究了增压涡轮用镍基高温合金 K418和 K419的凝固特性和热裂倾向性。同时研究了合金元素的偏析行为和析出相。结果表明，凝固末期多种强枝晶间偏析元素在液相中的偏聚导致 K419合金的凝固行为较 K418复杂。多种元素在枝晶间剩余液相中的偏聚导致K419合金的液相线极低。K419合金凝固过程中漫长的剩余液相期的存在严重削弱了枝晶间结合力，增加了其热裂倾向性。基于一种热裂敏感区模型提出热裂倾向性系数判据， K419合金的热裂倾向性系数高于K418合金。