高温合金单晶铸造中凝固条件的时空变化及对杂晶缺陷的影响
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摘要
在真空定向凝固炉中进行了两种高温合金的单晶凝固试验,通过金相检查检验了杂晶缺陷形成的特点,发现杂晶的产生倾向与合金种类及在铸件中的相对位置有关。试验中还测量了铸件下部和上部多个特征点的冷却曲线,分析了铸件中的凝固条件随时间和空间发生的变化。发现铸件下部在激冷效应消失后,凝固速度VS远低于抽拉速度VW,凝固界面处于炉底隔热区内;而在凝固后期的铸件上部则完全相反,VS远高于VW,凝固界面上升进入加热区。总体来说,铸件的上部比下部更易产生杂晶。型壳串中每个铸件由于内外两侧传热条件不同造成组织缺陷的不对称:在铸件下部,外侧比内侧更易产生杂晶,而在上部则相反,这是因为在工艺过程中凝固条件不对称的方向发生了转化。
Single crystal(SC) components of the superalloys DZ445 and MM 247 were produced in a productionscale Bridgman furnace. Through metallographic observation for the components, it was found that the formation tendency of stray grain defect was dependent not only on the type of alloy, but also on their positions in the castings. Under the same production conditions, the castings made from alloy MM 247 were more prone to stray formation than alloy DZ445. In a casting cluster, more stray grains were observed in the upper platforms than in the lower ones. The asymmetric thermal conditions between the inside and outside of the cluster caused the asymmetrical formation of spray grain defects. The temperatures in the important positions were measured to determine the time and space dependent changes of the asymmetric solidification condition in the castings. After the rapid solidification in the starting zone due to the quenching effect of the chill plate, the solidification velocity VS reduced quickly and became lower than the withdrawal velocity VW.The solidification front remained in the baffle zone. During the withdrawal process, the furnace bottom was more and more opened, leading to the undesired cooling in the middle zone of the mold cluster. During the solidification of the upper parts of the casting cluster, VS became much higher than VW, and the solidification front moved upwards into the heating zone of the furnace. This was an unfavorable thermal condition for the SC growth in the upper portion, especially in the inside of the casting cluster.
Single crystal(SC) components of the superalloys DZ445 and MM 247 were produced in a productionscale Bridgman furnace. Through metallographic observation for the components, it was found that the formation tendency of stray grain defect was dependent not only on the type of alloy, but also on their positions in the castings. Under the same production conditions, the castings made from alloy MM 247 were more prone to stray formation than alloy DZ445. In a casting cluster, more stray grains were observed in the upper platforms than in the lower ones. The asymmetric thermal conditions between the inside and outside of the cluster caused the asymmetrical formation of spray grain defects. The temperatures in the important positions were measured to determine the time and space dependent changes of the asymmetric solidification condition in the castings. After the rapid solidification in the starting zone due to the quenching effect of the chill plate, the solidification velocity VS reduced quickly and became lower than the withdrawal velocity VW.The solidification front remained in the baffle zone. During the withdrawal process, the furnace bottom was more and more opened, leading to the undesired cooling in the middle zone of the mold cluster. During the solidification of the upper parts of the casting cluster, VS became much higher than VW, and the solidification front moved upwards into the heating zone of the furnace. This was an unfavorable thermal condition for the SC growth in the upper portion, especially in the inside of the casting cluster.
引文
[1]Paul U,Sahm P R,Goldschmidt D. Inhomogeneties in single-crystal components[J]. Mat. Sci. Eng. 1993,A173:49-54.
[2]Cockcroft S L,Rappaz M,Mitchell A,et al. An examination of some of the manufacturing problems of large single-crystal turbine blades for used in land-based gas turbines[C]//Material for Advanced Power Engineering 1994,Liege,Belgium,1994:1145-1154.
[3]Meyer ter Vehn M,Dedecke D,Paul U. et al. Undercoolingrelated casting defects in single crystal turbine blades[M]. Superalloys 1996,Eds. R.D. Kissinger et al,TMS,1996:471-479.
[4]Ma D,Bührig-Polaczek A. Application of heat-conductor technique to production of single crystal turbine blade[J]. Metall. Mater. Trans,2009,B 40:738-748.
[5]Ma D,Wu Q,Bührig-Polaczek A. Investigation on the asymmetry of thermal condition and grain defect formation in customary directional solidification process[J]. IOP Conf. Series:Materials Science and Engineering,2011,27:012037.
[6]张小丽,周亦胄,金涛,等.镍基单晶高温合金杂晶形成倾向性的研究[J].金属学报,2012,48(10):1229-1236.
[7]刘林.高温合金精密铸造技术研究进展[J].铸造,2012,61(11):1273-1285.
[8]张宏琦,张军,李亚峰,等.一种第三代镍基单晶高温合金铸件截面突变处的杂晶形成过程[J].铸造,2014,63(2):128-137.
[9]Ma D,Zhou B,Bührig-Polaczek A. Investigation of heat conductor technique to produce single crystal turbine blades of middle size[J].Int. Foundry Research,2010,62:32-40.
[10]Ma D,Wu Q,Bührig-Polaczek A. Undercoolability of superalloys and solidification defects in single crystal components[J]. Advanced Materials Research,2011,278:417-422.
[11]Pollock T M,Murphy W H. The Breakdown of single-crystalSolidification in high refractory Ni-base alloys[J]. Metall. Trans,1996,A27:1081-1094.
[12]Ma D. Production and simulation of large single crystal turbine blades[J]. Giessereiforschung,2001,53:36-41.
[13]Ma D,Bührig-Polaczek A. Avoiding grain defects in single crystal components by using heat-conductor technique[J]. Int. J. Met. Res.(Z.Metallkunde),2009,100:1145-1151.
[14]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.
[15]Ma D,Wu Q,Bührig-Polaczek A. The geometry effect of freckle formation in the directionally solidified superalloy CMSX-4[J]. Metall.Mater. Trans. A, 2014,45A:1435-1444.
[16]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.
[17]Ma D,Wang F,Wu Q. et al. Temperature evolution and grain defect formation during single crystal solidification of blade cluster[J].China Foundry,2017,14(5):456-460.
[2]Cockcroft S L,Rappaz M,Mitchell A,et al. An examination of some of the manufacturing problems of large single-crystal turbine blades for used in land-based gas turbines[C]//Material for Advanced Power Engineering 1994,Liege,Belgium,1994:1145-1154.
[3]Meyer ter Vehn M,Dedecke D,Paul U. et al. Undercoolingrelated casting defects in single crystal turbine blades[M]. Superalloys 1996,Eds. R.D. Kissinger et al,TMS,1996:471-479.
[4]Ma D,Bührig-Polaczek A. Application of heat-conductor technique to production of single crystal turbine blade[J]. Metall. Mater. Trans,2009,B 40:738-748.
[5]Ma D,Wu Q,Bührig-Polaczek A. Investigation on the asymmetry of thermal condition and grain defect formation in customary directional solidification process[J]. IOP Conf. Series:Materials Science and Engineering,2011,27:012037.
[6]张小丽,周亦胄,金涛,等.镍基单晶高温合金杂晶形成倾向性的研究[J].金属学报,2012,48(10):1229-1236.
[7]刘林.高温合金精密铸造技术研究进展[J].铸造,2012,61(11):1273-1285.
[8]张宏琦,张军,李亚峰,等.一种第三代镍基单晶高温合金铸件截面突变处的杂晶形成过程[J].铸造,2014,63(2):128-137.
[9]Ma D,Zhou B,Bührig-Polaczek A. Investigation of heat conductor technique to produce single crystal turbine blades of middle size[J].Int. Foundry Research,2010,62:32-40.
[10]Ma D,Wu Q,Bührig-Polaczek A. Undercoolability of superalloys and solidification defects in single crystal components[J]. Advanced Materials Research,2011,278:417-422.
[11]Pollock T M,Murphy W H. The Breakdown of single-crystalSolidification in high refractory Ni-base alloys[J]. Metall. Trans,1996,A27:1081-1094.
[12]Ma D. Production and simulation of large single crystal turbine blades[J]. Giessereiforschung,2001,53:36-41.
[13]Ma D,Bührig-Polaczek A. Avoiding grain defects in single crystal components by using heat-conductor technique[J]. Int. J. Met. Res.(Z.Metallkunde),2009,100:1145-1151.
[14]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.
[15]Ma D,Wu Q,Bührig-Polaczek A. The geometry effect of freckle formation in the directionally solidified superalloy CMSX-4[J]. Metall.Mater. Trans. A, 2014,45A:1435-1444.
[16]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.
[17]Ma D,Wang F,Wu Q. et al. Temperature evolution and grain defect formation during single crystal solidification of blade cluster[J].China Foundry,2017,14(5):456-460.
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