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金属学报  2020, Vol. 56 Issue (3): 301-310    DOI: 10.11900/0412.1961.2019.00287
  研究论文 本期目录 | 过刊浏览 |
高温合金单晶铸件中条纹晶的形成机制
马德新1,2,王富3,徐维台1,徐文梁3,赵运兴1()
1. 深圳万泽中南研究院 深圳 518045
2. 中南大学粉末冶金研究院 长沙 410083
3. 西安交通大学机电工程学院 西安 710049
Formation of Sliver Defects in Single CrystalCastings of Superalloys
MA Dexin1,2,WANG Fu3,XU Weitai1,XU Wenliang3,ZHAO Yunxing1()
1. Wedge Central South Research Institute, Shenzhen 518045, China
2. Powder Metallurgy Research Institute, Central South University, Changsha 410083, China
3. School of Mechanic and Electronic Engineering, Xi’an Jiao Tong University, Xi’an 710049, China
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摘要: 

对高温合金单晶叶片铸件中条纹晶起源处的微观组织进行了观察分析,提出了这种晶粒缺陷的产生机理。通过微观检测确认了条纹晶的出现是由于铸件表面单个枝晶主干在糊状区内被撕断,但又被残余液体焊合,呈现出明显的起点。导致这种撕裂的主要原因是型壳粘连引起的枝晶收缩严重受阻或是由夹杂切割引起的枝晶强度严重受损,从而形成了条纹晶缺陷产生的2种主要机制。撕裂后的枝晶会发生一定程度的整体偏转,在基体组织上形成一个由小角度晶界封闭而成的狭长晶粒。比较了条纹晶与其它晶粒缺陷的相似和不同之处,并讨论了减少条纹晶缺陷应该采取的工艺措施。

关键词 条纹晶高温合金单晶叶片晶体缺陷    
Abstract

In the casting components of superalloys with increasing content of the refractory elements the occurrence of sliver defects becomes rather frequent. In comparison to the other grain defects such as stray grains and freckles, the sliver defect was less well understood and its formation mechanism is still unclear. In the present work, the origins of the sliver defects in the single crystal (SC) castings were investigated. In the metallographic detection, sliver grains can be identified to be miss-alignments of isolated, individual primary dendrite on the SC matrix. The sliver defects originated from the tearing of the existing dendrite stems in the mush zone, revealing a clear starting point of sliver defect. The cracks of the dendrites were filled by the interdendritic residual melt, which finally solidified into γ′-stripes. The tearing of some existing dendrite stems can be attributed to the adhesion of shell mold that hinders the shrinkage of the columnar dendrites on the casting surface. The second reason for the dendrite tearing is the insertion of oxide residues which significantly weakens the strength of the dendrite stems. Due to the support of the neighboring columnar dendrites, the tilting of the broken dendrites is limited, so that the grain boundary between a sliver and the matrix structure has normally a low angle. The structure and formation mechanisms of sliver defects were discussed in comparison with other defects such as stray grains, freckles and low angle grain boundaries. The corresponding methods were proposed to avoid sliver defects in production of SC superalloy castings.

Key wordssliver    superalloy    single crystal    grain defect
收稿日期: 2019-09-02     
ZTFLH:  TG146  
基金资助:国家自然科学基金项目(91860103);深圳科技创新委员会项目(20150128085205453)
通讯作者: 赵运兴     E-mail: sunwq@wedge.com.cn
Corresponding author: Yunxing ZHAO     E-mail: sunwq@wedge.com.cn
作者简介: 马德新,男,1955年生,教授,博士

引用本文:

马德新,王富,徐维台,徐文梁,赵运兴. 高温合金单晶铸件中条纹晶的形成机制[J]. 金属学报, 2020, 56(3): 301-310.
Dexin MA, Fu WANG, Weitai XU, Wenliang XU, Yunxing ZHAO. Formation of Sliver Defects in Single CrystalCastings of Superalloys. Acta Metall Sin, 2020, 56(3): 301-310.

链接本文:

https://www.ams.org.cn/CN/10.11900/0412.1961.2019.00287      或      https://www.ams.org.cn/CN/Y2020/V56/I3/301

AlloyCrCoWMoAlTiTaHfReNi
DD57.027.525.031.526.23-6.510.153.01Bal.
CMSX-46.499.716.410.635.601.016.520.102.97Bal.
表1  所用合金的的化学成分 (mass fraction / %)
图1  叶片上起源于Pt丝芯撑和凸包部位的条纹晶
图2  叶片上的条纹晶缺陷及其OM放大图和SEM像
图3  另一例条纹晶缺陷及起源处的放大OM像
图4  叶片上起源于氧化夹杂的条纹晶
图5  条纹晶缺陷及其起源处的OM像和SEM像
图6  图5e中试样截面的EDS扫描结果
图7  模壳粘连引起条纹晶的示意图
图8  夹杂嵌入枝晶引起条纹晶的示意图
图9  枝晶横向收缩(包括法向和切向收缩)引起的条纹晶产生机制示意图
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