高温合金单晶铸件中条纹晶缺陷的试验研究
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摘要
对几种高温合金铸件中的条纹晶缺陷进行了考察和分析。发现条纹晶多出现于竖直的叶身部位,叶背多于叶盆,上部多于下部,而叶根(榫头)部位极少出现。在竖直的叶身部位的条纹晶多是纵向生长,但也有的是斜向发展。而处于水平状态的叶冠或缘板上会出现横向的条纹晶缺陷。所有条纹晶都是在基体枝晶组织的基础上形成,其基本走向由基体枝晶决定,不论这些枝晶是纵向、斜向还是横向。条纹晶不仅是是细长的线形缺陷,也可能发展为大尺度的三维缺陷,严重影响单晶铸件的质量。从铸件的微观组织来看,条纹晶实际上起源于单晶基体上断裂出来的一段枝晶。
This paper presents the observations on the sliver defects in the single crystal(SC) castings of some Nibased superalloys. It was found that the slivers occurred most frequently on the blade bodies, especially on their convex sides and upper positions. In comparison, fewer slivers were observed in blade foot. Beside the vertical ones, tilted slivers were also observed. On the horizontally positioned platforms, however, lateral slivers were formed because of the matrix dendrites grown in the same direction. That means the alignment of the slivers is not always along the axis of the blades, but determined by the orientation of the local matrix dendrites, no matter it is vertical, tilted or lateral. Sometimes a narrow sliver can develop into 3-dementional defect of large scale, hence becoming a serious grain defect in SC casting. In the metallographic detection,sliver grain can be identified to be mis-alignments of isolated, individual primary dendrite stems on the SC matrix. The mechanism of sliver formation should be further studied in the next work.
This paper presents the observations on the sliver defects in the single crystal(SC) castings of some Nibased superalloys. It was found that the slivers occurred most frequently on the blade bodies, especially on their convex sides and upper positions. In comparison, fewer slivers were observed in blade foot. Beside the vertical ones, tilted slivers were also observed. On the horizontally positioned platforms, however, lateral slivers were formed because of the matrix dendrites grown in the same direction. That means the alignment of the slivers is not always along the axis of the blades, but determined by the orientation of the local matrix dendrites, no matter it is vertical, tilted or lateral. Sometimes a narrow sliver can develop into 3-dementional defect of large scale, hence becoming a serious grain defect in SC casting. In the metallographic detection,sliver grain can be identified to be mis-alignments of isolated, individual primary dendrite stems on the SC matrix. The mechanism of sliver formation should be further studied in the next work.
引文
[1]PAUL U,SAHM P R,GOLDSCHMIDT D. Inhomogeneties in single-crystal components[J]. Mat. Sci. Eng. 1993,A173:49-54.
[2]MEYER Ter Vehn M,DEDECKE D,PAUL U,et al. Undercooling related casting defects in single crystal turbine blades[C]//Superalloys,1996,Eds. R.D. Kissinger et al,TMS,1996:471-479.
[3]马德新.高温合金叶片单晶凝固技术新发展[J].金属学报,2015,51(10):1179-1190.
[4]马德新,张琼元,王海洋,等.工艺条件对镍基高温合金DD483的单晶叶片中杂晶缺陷的影响[J].铸造,2017,66(5):439-444.
[5]GIAMEI A F,KEAR B H. On the nature of freckles in nickel base superalloys[J]. Metall. Trans. 1970(1):2185-2192.
[6]MA D,WU Q,BüHRIG-POLACZEK A. Some new observations on freckle formation in directionally solidified superalloy components[J].Metall. Mater. Trans. 2012,43B:344-353.
[7]TIN S,POLLOCK T M. Predicting freckle formation in single crystal Ni-base superalloys[J]. J. Materials Science,2004,39:7199-7205.
[8]AUBURTIN P,WANG T,COCKCROFT S L. Freckle formation and freckle criterion in superalloy castings[J]. Metall. Mater. Trans. B,2000,31:801-811.
[9]马德新.定向凝固的复杂形状高温合金铸件中的雀斑形成[J].金属学报, 2016,52(4):426-436.
[10]CARNEY C A,BEECH J. The origin of sliver defects in single crystal turbine blades[C]//Solidification Processing 1987,Institute of Metals,London,33-36.
[11]史振学,刘世忠,李嘉荣.单晶高温合金定向凝固过程中条带的形成机制[J].热加工工艺,2013,42(13):31-33.
[12]AVESON J W,TENANT P A,FOSS B J,et al. On the origin of sliver defect in single crystal investment castings[J]. Act. Mat. 2013,61:5262-5171.
[2]MEYER Ter Vehn M,DEDECKE D,PAUL U,et al. Undercooling related casting defects in single crystal turbine blades[C]//Superalloys,1996,Eds. R.D. Kissinger et al,TMS,1996:471-479.
[3]马德新.高温合金叶片单晶凝固技术新发展[J].金属学报,2015,51(10):1179-1190.
[4]马德新,张琼元,王海洋,等.工艺条件对镍基高温合金DD483的单晶叶片中杂晶缺陷的影响[J].铸造,2017,66(5):439-444.
[5]GIAMEI A F,KEAR B H. On the nature of freckles in nickel base superalloys[J]. Metall. Trans. 1970(1):2185-2192.
[6]MA D,WU Q,BüHRIG-POLACZEK A. Some new observations on freckle formation in directionally solidified superalloy components[J].Metall. Mater. Trans. 2012,43B:344-353.
[7]TIN S,POLLOCK T M. Predicting freckle formation in single crystal Ni-base superalloys[J]. J. Materials Science,2004,39:7199-7205.
[8]AUBURTIN P,WANG T,COCKCROFT S L. Freckle formation and freckle criterion in superalloy castings[J]. Metall. Mater. Trans. B,2000,31:801-811.
[9]马德新.定向凝固的复杂形状高温合金铸件中的雀斑形成[J].金属学报, 2016,52(4):426-436.
[10]CARNEY C A,BEECH J. The origin of sliver defects in single crystal turbine blades[C]//Solidification Processing 1987,Institute of Metals,London,33-36.
[11]史振学,刘世忠,李嘉荣.单晶高温合金定向凝固过程中条带的形成机制[J].热加工工艺,2013,42(13):31-33.
[12]AVESON J W,TENANT P A,FOSS B J,et al. On the origin of sliver defect in single crystal investment castings[J]. Act. Mat. 2013,61:5262-5171.