高合金化GH4065镍基变形高温合金点状偏析研究
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摘要
以真空感应熔炼+电渣重熔+真空自耗重熔三联冶炼GH4065高合金化镍基变形高温合金棒材(直径280 mm)为对象,系统研究了该合金点状偏析的低倍组织、元素分布、第二相及晶粒形貌,分析了典型溶质元素对点状偏析行为的影响,探讨点状偏析的形成规律与机制及控制思路。结果表明,GH4065合金点状偏析主要源于枝晶间富Ti、Nb等元素的熔体密度较小冲破枝晶臂流动形成的通道偏析;锻造后生成较多的板条状η相、块状M_3B_2型硼化物与MC型碳化物。热力学相计算亦证实了点状偏析区较正常组织区域更容易生成η相、M_3B_2和MC。热处理后,与正常组织区域相比,点状偏析中仍存在板条状η相,一次γ′相的尺寸和数量明显增加,二次γ′相尺寸和形貌基本相同但数量减少。分析发现,由于点状偏析区的成分变化使得γ′相回溶温度升高,导致锻造中粗大γ′相阻碍再结晶长大,点状偏析区晶粒尺寸小于正常组织区域。采取前道次冶炼精细化控制、释放电极残余应力、适度降低真空自耗重熔熔化速率、加强真空自耗重熔冷却等措施,可以有效降低点状偏析的形成倾向。
GH4065 alloy is a new type of high-alloyed wrought superalloy, in which freckle defect is extremely prone to form in large ingot. In the present research, the freckle of GH4065 alloy bar with the diameter of 280 mm produced by vacuum induction melting(VIM)+electroslag remelting(ESR)+vacuum arc remelting(VAR) triple smelting was studied. The macrostructure, secondary phases and grain structure of the freckle were investigated, the influences of solute elements on the freckle were analyzed, and both the mechanism and control methods were also discussed. The results show that the freckle in GH4065 alloy is caused by channel segregation with the low-density Ti and Nb-rich melt flows. Additionally, lots of lath-like η-phases, block M3 B2 borides and MC carbides are formed in the forged condition. It is confirmed by the thermodynamic calculations that the η-phases, M3 B2 borides and MC carbides are much easier forming in the freckle than that in matrix. After heat treatment, compared with matrix, the lathy η-phases are still existed in the freckle; the size and quantity of primary γ ′ phases increase significantly while the size and morphology of the secondary γ ′ phase are basically identical, only with less quantity. It has been found that due to the high content of γ ′ phase, the γ ′ dissolution temperature in the freckle is higher than that in the matrix. This induces an impeded recrystallization process caused by the coarsened γ ′ phases during forging process and the grain size of the freckle region is significantly smaller than that of matrix. Based on this study, the formation of freckle can be effectively controlled by meticulous controlling of the previous smelting process, releasing of electrode residual stress, suitably reducing VAR melting rate, and accelerating VAR cooling.
GH4065 alloy is a new type of high-alloyed wrought superalloy, in which freckle defect is extremely prone to form in large ingot. In the present research, the freckle of GH4065 alloy bar with the diameter of 280 mm produced by vacuum induction melting(VIM)+electroslag remelting(ESR)+vacuum arc remelting(VAR) triple smelting was studied. The macrostructure, secondary phases and grain structure of the freckle were investigated, the influences of solute elements on the freckle were analyzed, and both the mechanism and control methods were also discussed. The results show that the freckle in GH4065 alloy is caused by channel segregation with the low-density Ti and Nb-rich melt flows. Additionally, lots of lath-like η-phases, block M3 B2 borides and MC carbides are formed in the forged condition. It is confirmed by the thermodynamic calculations that the η-phases, M3 B2 borides and MC carbides are much easier forming in the freckle than that in matrix. After heat treatment, compared with matrix, the lathy η-phases are still existed in the freckle; the size and quantity of primary γ ′ phases increase significantly while the size and morphology of the secondary γ ′ phase are basically identical, only with less quantity. It has been found that due to the high content of γ ′ phase, the γ ′ dissolution temperature in the freckle is higher than that in the matrix. This induces an impeded recrystallization process caused by the coarsened γ ′ phases during forging process and the grain size of the freckle region is significantly smaller than that of matrix. Based on this study, the formation of freckle can be effectively controlled by meticulous controlling of the previous smelting process, releasing of electrode residual stress, suitably reducing VAR melting rate, and accelerating VAR cooling.
引文
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[20]Zhang B J,Zhao G P,Zhang W Y,et al.Deformation mechanisms and microstructural evolution ofγ+γ′duplex aggregates generated during thermomechanical processing of nickel-base superalloys[A].Superalloys 2016[C].Pittsburgh:TMS,2016:487
[21]Wlodek S T,Kelly M,Alden D A.The structure of René88DT[A].Superalloys 1996[C].Pittsburgh:TMS,1996:129
[22]Heaney J,Lasonde M,Powell A,et al.Development of a new cast and wrought alloy(René65)for high temperature disk applica‐tions[A].8th International Symposium on Superalloy 718 and De‐rivatives[C].Pittsburgh:TMS,2014:67
[23]Schafrik R E.Materials for a non-steady-state world[J].Metall.Mater.Trans.,2016,47A:2539
[24]Crozet C,Devaux A,Forestier R,et al.Effect of ingot size on mi‐crostructure and properties of the new advanced AD730TMsuperal‐loy[A].Superalloys 2016[C].Pittsburgh:TMS,2016:437
[25]Moyer J M,Jackman L A,Adasczik C B,et al.Advances in triple melting[A].Superalloys 718,625,706 and Various Derivatives[C].Pittsburgh:TMS,1994:39
[2]Devaux A,Georges E,Héritier P.Development of new C&W su‐peralloys for high temperature disk applications[J].Adv.Mater.Res.,2011,278:405
[3]Jiang H F.Requirements and forecast of turbine disk materials[J].Gas Turb.Exp.Res.,2002,15(4):1(江和甫.对涡轮盘材料的需求及展望[J].燃气涡轮试验与研究,2002,15(4):1)
[4]Wang X D,Wang H C.Improved development superalloys,pro‐mote the aero-engine development[A].The Thirteenth Session of the Annual China Superalloys Conference[C].Beijing:Metallurgi‐cal Industry Press,2015:3(王旭东,王海川.改进发展高温合金,推动航空发动机研制[A].第十三届中国高温合金年会论文集[C].北京:冶金工业出版社,2015:3)
[5]Williams J C,Starke E A Jr.Progress in structural materials for aerospace systems[J].Acta Mater.,2003,51:5775
[6]Zhang B J,Zhao G P,Zhang W Y,et al.Investigation of high per‐formance disc alloy GH4065 and associated advanced processing techniques[J].Acta Metall.Sin.,2015,51:1227(张北江,赵光普,张文云等.高性能涡轮盘材料GH4065及其先进制备技术研究[J].金属学报,2015,51:1227)
[7]Du J H,Zhao G P,Deng Q,et al.Development of wrought superal‐loy in China[J].J.Aeron.Mater.,2016,36(3):27(杜金辉,赵光普,邓群等.中国变形高温合金研制进展[J].航空材料学报,2016,36(3):27)
[8]Donachie M J,Donachie S J.Superalloys:A Technical Guide[M].2nd Ed.,Materials Park,OH:ASM International,2002:41
[9]Dong J X,Zhang M C,Zeng Y P.Freckle formation mechanism and its criterion[J].Ordn.Mater.Sci.Eng.,2005,28(1):1(董建新,张麦仓,曾燕屏."黑斑"形成机理及判据[J].兵器材料科学与工程,2005,28(1):1)
[10]Zhong Z Y,Zhuang J Y.Development of several important prob‐lems on producing technologies of wrought superalloy[J].J.Iron Steel Res.,2003,15(7):1(仲增墉,庄景云.变形高温合金生产工艺中几个重要问题的研究和进展[J].钢铁研究学报,2003,15(7):1)
[11]Auburtin P,Wang T,Cockcroft S L,et al.Freckle formation and freckle criterion in superalloy castings[J].Metall.Mater.Trans.,2000,31B:801
[12]Genereux D P,Borg A C.Characterization of freckles in a high strength wrought nickel superalloy[A].Superalloys 2000[C].Pittsburgh:TMS,2000:19
[13]Dai P C,Wei Z G,Wang Z X,et al.The microstructure analysis and formation mechanism research for freckle defect of a Ni-based superalloy[J].Bao-Steel Technol.,2015,(5):49(代朋超,魏志刚,王资兴等.一种镍基高温合金黑斑缺陷的组织分析及形成机理研究[J].宝钢技术,2015,(5):49)
[14]Dong J X,Zhang M C,Zeng Y P.Microstructure behavior and freckle characteristics for GH706 superalloy[J].Rare Met.Mater.Eng.,2006,35:176(董建新,张麦仓,曾燕屏.Inconel 706合金宏观偏析"黑斑"的形成特征及组织行为[J].稀有金属材料与工程,2006,35:176)
[15]Van Den Avyle J A,Brooks J A,Powell A C.Reducing defects in remelting processes for high-performance alloys[J].JOM,1998,50(3):22
[16]Auburtin P,Cockcroft S L,Mitchell A.Liquid density inversions during the solidification of superalloys and their relationship to freckle formation in castings[A].Superalloy 1996[C].Pittsburgh:TMS,1996:443
[17]Schneider M C,Gu J P,Beckermann C,et al.Modeling of microand macrosegregation and freckle formation in single-crystal nickel-base superalloy directional solidification[J].Metall.Mater.Trans.,1997,28A:1517
[18]Auburtin P,Cockcroft S L,Mitchell A,et al.Freckle formation in superalloys[A].Superalloys 2000[C].Pittsburgh:TMS,2000:255
[19]Han Z Q,Liu B C.Numerical simulation on channel segregation in vertically unidirectional solidification process[J].Acta Metall.Sin.,2003,39:140(韩志强,柳百成.垂直定向凝固条件下通道偏析形成过程的数值模拟[J].金属学报,2003,39:140)
[20]Zhang B J,Zhao G P,Zhang W Y,et al.Deformation mechanisms and microstructural evolution ofγ+γ′duplex aggregates generated during thermomechanical processing of nickel-base superalloys[A].Superalloys 2016[C].Pittsburgh:TMS,2016:487
[21]Wlodek S T,Kelly M,Alden D A.The structure of René88DT[A].Superalloys 1996[C].Pittsburgh:TMS,1996:129
[22]Heaney J,Lasonde M,Powell A,et al.Development of a new cast and wrought alloy(René65)for high temperature disk applica‐tions[A].8th International Symposium on Superalloy 718 and De‐rivatives[C].Pittsburgh:TMS,2014:67
[23]Schafrik R E.Materials for a non-steady-state world[J].Metall.Mater.Trans.,2016,47A:2539
[24]Crozet C,Devaux A,Forestier R,et al.Effect of ingot size on mi‐crostructure and properties of the new advanced AD730TMsuperal‐loy[A].Superalloys 2016[C].Pittsburgh:TMS,2016:437
[25]Moyer J M,Jackman L A,Adasczik C B,et al.Advances in triple melting[A].Superalloys 718,625,706 and Various Derivatives[C].Pittsburgh:TMS,1994:39