航空学报 > 1986, Vol. 7 Issue (2): 181-186

凝固参数对定向镍基铸造高温合金中MC碳化物生长特性的影响

刘林, 傅恒志, 史正兴   

  1. 西北工业大学
  • 收稿日期:1985-07-15 修回日期:1900-01-01 出版日期:1986-04-25 发布日期:1986-04-25

THE EFFECT OF SOLIDIFICATION PARAMETERS ON THE GROWTH BEHAVIOR OF MC CARBIDES IN DIRECTSONALLY SOLIDIFIED NICKEL BASE SUPERALLOYS

Liu Lin, Fu Hengzhi, Shi Zhengxing   

  1. North-western Polytechnical University
  • Received:1985-07-15 Revised:1900-01-01 Online:1986-04-25 Published:1986-04-25

摘要: 本文研究了定向凝固条件下凝固参数对一种镍基铸造高温合金中MC碳化物的形态、数量和分布的影响。在冷却速率很小的平面界面下,少量MC呈块状八面体;当界面转化为胞状时,MC在胞晶间呈长条状或鱼骨状;对于冷却速率较大的树枝状组织,MC则呈粗大的汉字体或较完整的花瓣状。在合金凝固形态由平面状向树枝状的转化过程中,合金中MC碳化物的数量急剧增多。

Abstract: The Chinese-script type carbides in cast Ni-base superalloys are considered detrimental to mechanical properties. Controlling the MC carbides, therefore, has been the main concern of metallurgists. A review of the literature has been shown that most previous studies on carbide in superalloys were confined to equiaxed and directionally solidified dendritic structures, and there is a lack of systematic study on the growth behavior of carbides under other solidification conditions. The intent of this paper is to present research on the corbide growth behaviors with various solid-liquid interfacial morphologies using directional solidification techniques, with the aim of improving the mechanical properties of the alloy by controlling the solidification parameters. The following results were obtained:( 1 ) In directionally solidified alloys with a planar interface, the precipitated MC carbides usually had an octahedral block appearance; with a cellular interface, an elongated or fishbone type precipitate was observed; the morphology changed to an anchor type during cellular-dendritic growth; and a highly developed Chinese-script and complete petal type morphology was observed during dendritic growth.(2) During the transition from a planar to a dendritic interface, the volume fraction of MC corbides increased significantly with the increase of cooling rate.Based on the results of this experiment, a growth mechanism of MC carbides from the melt has been proposed. It is considerd that the segregation behavior of elements in the interdendritic liquid is the controlling factor for the subsequent nucleation and growth of the MC carbides. It is therefore necessary to control the formation of MC carbide through controlling the growth morphology of primary r phase and the interdendritic microsegregation. By adjusting the cooling rate this goal can be achieved conveniently and practically.