几种镍基高温合金的过冷能力和单晶可铸性的研究与比较
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摘要
对6种镍基高温合金熔体在陶瓷型壳中的凝固行为进行了检测,得出了各种合金的液相线温度T_L、临界形核温度TN和临界形核过冷度ΔT_N=T_L-T_N,发现它们具有明显不同的过冷能力。在单晶叶片的铸造实验中,具有高过冷能力(高于40℃)的合金在宏观上抗杂晶能力最强,但容易形成枝晶碎臂微观缺陷。具有中等过冷能力(20～30℃)的合金,既能有效防止宏观杂晶缺陷的发生,又能避免微观碎晶的形成,显示出最佳的单晶可铸性。而具有很低过冷能力(低于10℃)的合金,抗杂晶能力非常弱,表现出很差的单晶可铸性。镍基高温合金具有相似的化学成分,却显示出明显不同的过冷能力和单晶可铸性,对其原因还需要做进一步的研究。
The undercoolability of Ni-base superalloys is an important physical property to determine its single crystal(SC) castability, because stray grains will be formed if the local undercooling at the component extremities exceeds the undercoolability of the used alloys. In the present work, both the undercoolability of 6 Ni-based superalloys and their SC castability were investigated during isothermal cooling processes and directional solidification, respectively. The undercooling behavior of the alloys during isothermal heating and cooling processes was investigated under the same process condition as the SC casting experiment. The liquidus temperature TL and the critical nucleation temperature TN of the alloys were measured, respectively. The average critical nucleation undercooling ΔTN=TL-TN was determined for each alloy. Using a Bridgman furnace the directional solidification experiments were carried out to cast SC turbine blades of the used alloys in the homemade shell molds. The alloy CMSX-6 with high undercoolability has the best capacity to avoid stray grains, but revealing also fragment of dendrite arms due to the rapid dendrite growth in deeply undercooled platforms. In the castings of the alloys with medium undercoolability, neither stray grains nor micro-defect were found, revealing a defect free SC structure. As expected, the alloy DD483 with low undercoolability is very difficult to be cast into SC blades without stray grain, exhibiting a very low SC castability. It is hard to understand why the investigated Ni-base superalloys have so different SC solidification behaviors in spite of their similar chemical compositions. Further investigation should be carried out to find a reasonable explanation.
The undercoolability of Ni-base superalloys is an important physical property to determine its single crystal(SC) castability, because stray grains will be formed if the local undercooling at the component extremities exceeds the undercoolability of the used alloys. In the present work, both the undercoolability of 6 Ni-based superalloys and their SC castability were investigated during isothermal cooling processes and directional solidification, respectively. The undercooling behavior of the alloys during isothermal heating and cooling processes was investigated under the same process condition as the SC casting experiment. The liquidus temperature TL and the critical nucleation temperature TN of the alloys were measured, respectively. The average critical nucleation undercooling ΔTN=TL-TN was determined for each alloy. Using a Bridgman furnace the directional solidification experiments were carried out to cast SC turbine blades of the used alloys in the homemade shell molds. The alloy CMSX-6 with high undercoolability has the best capacity to avoid stray grains, but revealing also fragment of dendrite arms due to the rapid dendrite growth in deeply undercooled platforms. In the castings of the alloys with medium undercoolability, neither stray grains nor micro-defect were found, revealing a defect free SC structure. As expected, the alloy DD483 with low undercoolability is very difficult to be cast into SC blades without stray grain, exhibiting a very low SC castability. It is hard to understand why the investigated Ni-base superalloys have so different SC solidification behaviors in spite of their similar chemical compositions. Further investigation should be carried out to find a reasonable explanation.
引文
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[12]MA D,ZHOU B,BüHRIG-POLACZEK A. Development and application of heat-conductor technique for SC components of superalloys[J]. Adv. Mat. Res.,2011,278:306-311.
[13]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 publishing,Mat. Sci. Eng.,2011,27:012-037.
[14]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.
[15]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.
[16]张军,黄太文,刘林,等.单晶高温合金凝固特性与典型凝固缺陷研究[J].金属学报,2015,51(10):1163-1178.
[17]XUAN W D,REN Z M,LI C,Experimental evidence of the effect of a high magnetic field on the stray grains formation in cross-section change region for Ni-based superalloy during directional solidification[J]. Metall. Mater. Trans.,2015,46A:1461-1466.
[18]XUAN W,HUAN L,LI C,et al. Effect of a high magnetic field on microstructures of Ni-based single crystal superalloy during seed melt-back[J]. Metall. Mater. Trans.,2016,47B:828-33.
[19]XUAN W D,REN Z M,LI C,et al. Formation of stray grain in cross section area for Ni-based superalloy during directional solidification[J],IOP publishing:Mater. Sci. Eng.,2011,27:012-035.
[20]XUAN W D,REN Z M,LIU H,et al. Formation of stray grains in directionally solidified Ni-based superalloy with cross-section change regions[J]. Mater. Sci. Forum,2011,747-748:535-539.
[21]LI Y,LIU L,HUANG T,et al.,The formation mechanism,influencing factors and processing control of stray grains in nickel-based single crystal superalloys[C]//Superalloys 2016,Proceeding of 13th Int. Symposium on Superalloys,Eds. M. Hardy et al,TMS,2016:293-301.
[22]MA D. Production and simulation of large single crystal turbine blades[J]. Giessereiforschung,2001,53:36-41.
[23]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.
[24]马德新,张琼元,王海洋,等.高温合金DD483熔体的过冷能力测量[J].铸造,2017,66(6):593-598.
[25]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.
[2]刘林.高温合金精密铸造技术研究进展[J].铸造,2012,61(11):1273-1285.
[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]MA D,WANG F,WU Q,et al. Innovations in casting techniques for single crystal turbine blades of superalloys[C]//Superalloys 2016:Proceeding of 13th Int. Symposium on Superalloys,Eds. M. Hardy et al.,TMS,2016:237-246.
[5]PAUL U,SAHM P R,GOLDSCHMIDT D. Inhomogeneties in single-crystal components[J]. Mat. Sci. Eng.,1993,A173:49-54.
[6]COCKCROFT S L,RAPPAZ M,MITCHELL A,et al. An examination of some manufacturing problems of large single-crystal turbine blades[C]//Proceeding of “Material for Advanced Power Engineering”,eds. D. Coutsouradis et al,Liege,B,1994:1145-154.
[7]MEYER ter Vehn M,DEDECKE D,PAUL U,et al. Undercooling related casting defects in single crystal turbine blades[C]//Superalloys1996,Proceeding of 8th int. Symposium on Superalloys,Eds. R.D. Kissinger et al,TMS,1996:471-479.
[8]MA D,BüHRIG-POLACZEK A. Avoiding grain defects in single crystal components by using heat-conductor technique[J]. Int. J. Met.Res.,2009,100:1145-1151.
[9]MA D,BüHRIG-POLACZEK A. Development of heat-conductor technique for single crystal components of superalloys[J]. Int. J. Cast Met. Res.,2009,22:422-429.
[10]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.
[11]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.
[12]MA D,ZHOU B,BüHRIG-POLACZEK A. Development and application of heat-conductor technique for SC components of superalloys[J]. Adv. Mat. Res.,2011,278:306-311.
[13]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 publishing,Mat. Sci. Eng.,2011,27:012-037.
[14]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.
[15]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.
[16]张军,黄太文,刘林,等.单晶高温合金凝固特性与典型凝固缺陷研究[J].金属学报,2015,51(10):1163-1178.
[17]XUAN W D,REN Z M,LI C,Experimental evidence of the effect of a high magnetic field on the stray grains formation in cross-section change region for Ni-based superalloy during directional solidification[J]. Metall. Mater. Trans.,2015,46A:1461-1466.
[18]XUAN W,HUAN L,LI C,et al. Effect of a high magnetic field on microstructures of Ni-based single crystal superalloy during seed melt-back[J]. Metall. Mater. Trans.,2016,47B:828-33.
[19]XUAN W D,REN Z M,LI C,et al. Formation of stray grain in cross section area for Ni-based superalloy during directional solidification[J],IOP publishing:Mater. Sci. Eng.,2011,27:012-035.
[20]XUAN W D,REN Z M,LIU H,et al. Formation of stray grains in directionally solidified Ni-based superalloy with cross-section change regions[J]. Mater. Sci. Forum,2011,747-748:535-539.
[21]LI Y,LIU L,HUANG T,et al.,The formation mechanism,influencing factors and processing control of stray grains in nickel-based single crystal superalloys[C]//Superalloys 2016,Proceeding of 13th Int. Symposium on Superalloys,Eds. M. Hardy et al,TMS,2016:293-301.
[22]MA D. Production and simulation of large single crystal turbine blades[J]. Giessereiforschung,2001,53:36-41.
[23]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.
[24]马德新,张琼元,王海洋,等.高温合金DD483熔体的过冷能力测量[J].铸造,2017,66(6):593-598.
[25]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.
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