LMC法定向凝固抽拉速率对DD488单晶高温合金组织和持久性能的影响
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摘要
研究了液态金属冷却(LMC)法定向凝固抽拉速率对DD488单晶高温合金组织和980℃/250 MPa持久性能的影响。结果表明:增大抽拉速率能够显著细化合金的枝晶组织,减小铸态共晶含量和γ'相尺寸。同时,随着抽拉速率的增大,标准热处理后的γ通道宽度减小,γ'相体积分数增加。抽拉速率较小时(5 mm/min),合金980℃/250 MPa持久寿命为70.3 h,随着抽拉速率提高至8 mm/min,持久寿命增大到107.5 h。DD488合金持久寿命的提高得益于在较高的抽拉速率下合金标准热处理组织中的γ'相体积分数增加,γ通道宽度减小,并且共晶组织基本消除。
Effect of withdrawal rate of liquid metal cooling( LMC) process on microstructure and stress-rupture property at 980 ℃/250 MPa of DD488 single crystal superalloy was investigated. The results show that the dendrite microstructure is refined,the eutectic content and γ'precipitate size is reduced with the increasing of withdrawal rate from 5 mm/min to 8 mm/min. Meanwhile,the width of γ channel decreases and the volume fraction of γ' precipitates after standard heat treatment increases with the increasing of withdrawal rate. The stress-rupture life at 980 ℃/250 MPa is 70. 3 h when the withdrawal rate is 5 mm/min,and it increases to 107. 5 h when the withdrawal rate is increased to8 mm/min. Due to the increase of the volume fraction of γ' precipitates,the decrease of the width of γ channel and the eliminating of the eutectic in the DD488 superalloy after the standard heat treatment,the stress-rupture life of the DD488 alloy improves significantly at a higher withdrawal rate.
Effect of withdrawal rate of liquid metal cooling( LMC) process on microstructure and stress-rupture property at 980 ℃/250 MPa of DD488 single crystal superalloy was investigated. The results show that the dendrite microstructure is refined,the eutectic content and γ'precipitate size is reduced with the increasing of withdrawal rate from 5 mm/min to 8 mm/min. Meanwhile,the width of γ channel decreases and the volume fraction of γ' precipitates after standard heat treatment increases with the increasing of withdrawal rate. The stress-rupture life at 980 ℃/250 MPa is 70. 3 h when the withdrawal rate is 5 mm/min,and it increases to 107. 5 h when the withdrawal rate is increased to8 mm/min. Due to the increase of the volume fraction of γ' precipitates,the decrease of the width of γ channel and the eliminating of the eutectic in the DD488 superalloy after the standard heat treatment,the stress-rupture life of the DD488 alloy improves significantly at a higher withdrawal rate.
引文
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[14]Liu C,Shen J,Zhang J,et al.Effect of withdrawal rates on microstructure and creep strength of a single crystal superalloy processed by LMC[J].Journal of Materials Science and Technology,2010,26(4):306-310.
[15]马文有,李树索,乔敏,等.热处理对镍基单晶高温合金微观组织和高温持久性能的影响[J].中国有色金属学报,2006,16(6):937-944.Ma Wenyou,Li Shusuo,Qiao Min,et al.Effect of heat treatment on microstructure and stress rupture life of Ni-base single crystal superalloy[J].The Chinese Journal of Nonferrous Metals,2006,16(6):937-944.
[2]Brundidge C,Van Drasek D,Wang B,et al.Structure refinement by a liquid metal cooling solidification process for single-crystal nickel-base superalloys[J].Metallurgical and Materials Transactions A,2012,43(3):965-976.
[3]张健,申健,卢玉章,等.燃气轮机用大型定向结晶铸件制备及组织与性能研究[J].金属学报,2010,46(11):1322-1326.Zhang Jian,Shen Jian,Lu Yuzhang,et al.Processing,microstructure and mechanical properties of large directionally solidified castings for industrial gas turbine applications[J].Acta Metallurgica Sinica,2010,46(11):1322-1326.
[4]Liu C,Li K,Shen J,et al.Improved castability of directionally solidified,Ni-based superalloy by the liquid metal cooling process[J].Metallurgical and Materials Transactions A,2012,43(2):405-409.
[5]Feng Q,Nandy T K,Tin S,et al.Solidification of high-refractory ruthenium-containing superalloys[J].Acta Materialia,2003,51(1):269-284.
[6]Heckl A,Neumeier S,G9ken M,et al.The effect of Re and Ru onγ/γ'microstructure,γ-solid solution strengthening and creep strength in nickel-base superalloys[J].Materials Science and Engineering:A,2011,528(9):3435-3444.
[7]傅恒志,郭景杰,刘林,等.先进材料定向凝固[M].北京:科学出版社,2008.
[8]Bouchard D,Kirkaldy J S.Prediction of dendrite arm spacings in unsteady-and steady-state heat flow of unidirectionally solidified binary alloys[J].Metallurgical and Materials Transactions B,1997,28(4):651-663.
[9]Ma D X,Sahm P R.Primary spacing in directional solidification[J].Metallurgical and Materials Transactions A,1998,29(3):1113-1119.
[10]张卫国,刘林,黄太文,等.高温度梯度定向凝固冷却速率对DZ4125合金γ'相的影响[J].金属学报,2009,45(5):592-596.Zhang Weiguo,Liu Lin,Huang Taiwen,et al.Effect of cooling rate onγ'precipitate of DZ4125 alloy under high thermal gradient directional solidification[J].Acta Metallurgica Sinica,2009,45(5):592-596.
[11]Murakumo T,Kobayashi T,Koizumi Y,et al.Creep behaviour of Nibase single-crystal superalloys with variousγ'volume fraction[J].Acta Materialia,2004,52(12):3737-3744.
[12]石倩颖.多组元作用对第四代镍基单晶高温合金组织和高温低应力蠕变行为的影响[D].北京:北京科技大学,2014.
[13]Pollock T M,Argon A S.Creep resistance of CMSX-3 nickel base superalloy single crystals[J].Acta Metallurgica Et Materialia,1992,40(1):1-30.
[14]Liu C,Shen J,Zhang J,et al.Effect of withdrawal rates on microstructure and creep strength of a single crystal superalloy processed by LMC[J].Journal of Materials Science and Technology,2010,26(4):306-310.
[15]马文有,李树索,乔敏,等.热处理对镍基单晶高温合金微观组织和高温持久性能的影响[J].中国有色金属学报,2006,16(6):937-944.Ma Wenyou,Li Shusuo,Qiao Min,et al.Effect of heat treatment on microstructure and stress rupture life of Ni-base single crystal superalloy[J].The Chinese Journal of Nonferrous Metals,2006,16(6):937-944.