C对一种镍基单晶高温合金组织与拉伸性能的影响-中国材料进展

文章信息/Info

Title:: The Influence of Carbon Contents on the Microstructure and Tensile Properties of a Ni-Based Single Crystal Superalloy

作者:: 陶岩; 李永梅; 谭子昊; 曹亮; 王新广; 1.辽宁石油化工大学机械工程学院，辽宁抚顺 113001 2.中国科学院金属研究所，辽宁沈阳 110006

Author(s):: Tao Yan; Li Yongmei; Tan Zihao; Cao Liang; Wang Xinguang; 1. School of Mechanical Engineering，Liaoning Petrochemical University，Fushun 113001，China 2. Institute of Metal and Research，Chinese Academy of Science，Shenyang 110006，China

Keywords:: Ni-based single crystal superalloy; turbine blades; tensile strength; carbides; directional solidification

摘要:: 研究了C元素对一种低成本第二代镍基单晶高温合金微观组织与拉伸变形行为的影响。结果表明，随着C含量增加，铸态合金枝晶间的共晶组织逐渐消失，MC型碳化物含量升高，而经标准热处理后，不同C含量合金的γ+γ′两相组织均无明显变化。当拉伸温度为800和1100 ℃时，C含量增加均导致合金的拉伸强度与塑性降低。尽管合金在高温拉伸变形中析出的颗粒状M6C型碳化物与γ′相为共格析出关系，有助于阻碍超位错切割γ′相，但位于枝晶间的MC型碳化物又将消耗大量Ta，W等难熔元素，进而削弱了基体的固溶强化效果，最终导致合金拉伸强度降低。此外，枝晶间骨架状MC型碳化物的存在促进了800 ℃拉伸时合金沿碳化物生长平面的解理断裂，并加速了合金在1100 ℃拉伸时的裂纹萌生与扩展，是合金塑性降低的主要原因。

Abstract:: The effect of carbon content on the microstructure, tensile properties and deformation behavior of a low-cost second-generation Ni-based single crystal superalloy was investigated. The results showed that the area fraction of eutectic microstructure in the interdendritic region decreased with the increase of carbon content, while the content of MC-type carbides increased correspondingly. After standard heat treatment, no significant difference was observed in γ+γ′ microstructure among alloys with varying carbon contents. For tensile properties at high temperature, the increase of carbon content led to a decrease in tensile strength and plasticity at both 800 and 1100 ℃. Although the blocky M6C-type carbides coherently precipitated from the matrix during the tensile deformation, which helped to hinder superdislocation cutting into the γ′. The precipitation MC carbides located in the interdendritic regions would consume a large number of refractory elements like Ta and W, which substantially weakened the solid solution strengthening effect of γ matrix,resulting in a reduction of tensile strength. The interdendritic skeletonlike MC carbides promoted the cleavage fracture along the carbides at 800 ℃ tension, and accelerated the micro-crack initiation and macro-crack extensionat 1100 ℃ tension, which were considered as the main reason for the decrease in the alloy‘’s plasticity.