固溶冷却方式对K325合金组织特征的影响规律
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摘要
采用扫描电子显微镜(SEM)、电子探针(EPMA)和差热分析(DTA)等研究了K325合金的铸态组织、凝固行为,以及固溶处理后不同冷却方式对合金组织的影响。结果表明:K325合金铸态组织呈典型枝晶结构,枝晶间分布有条、块状富Nb和Ti的MC型碳化物,其面积分数约0.65%;合金凝固顺序为:L→L+γ→L+γ+MC→γ+MC。采用水冷冷却方式,碳化物主要分布于晶内,其数量和尺寸最小;采用空气冷却,碳化物仍主要分布于晶内,但碳化物数量和尺寸略有提高;采用随炉冷却,二次碳化物沿晶界连续析出,且数量和尺寸显著增加,同时在晶内形成八面体状的MC型碳化物。K325合金固溶处理后采用水冷冷却较为合理。
The effects of solid-solution heat treatment by various cooling method on microstructures of the Ni-based superalloy K325 were investigated,as well as the microstructure of as-cast specimen and solidification behavior by EPM A,DTA and SEM equipped with an EDS detector. The results indicated that a typical dendritic structure was clearly displayed in the as-cast sample. The stripy and blocky MC-type carbides highly enriching in Nb and Ti were observed in interdendritic volumes,and the area fraction was about 0. 65%. The solidification sequence of the alloy can be written as L → L + γ → L + γ + MC → γ + MC according to the DTA experiment result. The area fraction and size of MC carbides,compared with water quenching method,increased slightly after air cooling. And MC carbides could be observed in grain interior mostly by above cooling method. Nevertheless,the secondary carbides precipitated along grain boundary continuously under furnace cooling condition,moreover,the proportion and size of which increased sharply. Additionally,considerable octahedral-shape MC carbides was observed in the intragranular. In conclusion,the water quench-ing was regard as the most reasonable cooling method.
The effects of solid-solution heat treatment by various cooling method on microstructures of the Ni-based superalloy K325 were investigated,as well as the microstructure of as-cast specimen and solidification behavior by EPM A,DTA and SEM equipped with an EDS detector. The results indicated that a typical dendritic structure was clearly displayed in the as-cast sample. The stripy and blocky MC-type carbides highly enriching in Nb and Ti were observed in interdendritic volumes,and the area fraction was about 0. 65%. The solidification sequence of the alloy can be written as L → L + γ → L + γ + MC → γ + MC according to the DTA experiment result. The area fraction and size of MC carbides,compared with water quenching method,increased slightly after air cooling. And MC carbides could be observed in grain interior mostly by above cooling method. Nevertheless,the secondary carbides precipitated along grain boundary continuously under furnace cooling condition,moreover,the proportion and size of which increased sharply. Additionally,considerable octahedral-shape MC carbides was observed in the intragranular. In conclusion,the water quench-ing was regard as the most reasonable cooling method.
引文
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[20]卜凡征,王学敏,陈琳,等.Ti-Nb-Mo微合金钢回火过程中纳米碳化物的析出行为及组织演变[J].材料热处理学报,2015,36(8):96-103.
[21]李亚敏.Co、Zr、Cu在K4169合金中作用的研究[D].兰州:兰州理工大学,2011.
[2]Stephen Floreen,Gerhard Fuchs,Walter Yang.The Metallurgy of Alloy 625[C]∥Superalloys718,625 and Various Derivatives.The Minerals,Metals&Materials Society.Warrendale,1994:13-37.
[3]张红斌.国外Inconel 625合金的进展[J].特钢技术,2000(3):69-80.
[4]Eiselstein H L,Tillack D J.The invention and definition of alloy 625[C]∥Superalloys 718,625 and Various Derivatives.The M inerals,M etals&M aterials Society.Warrendale,1991:1-14.
[5]Cieslak M J,Headley T J,Romig A D,et al.A melting and solidification study of alloy 625[J].M etallurgical Transactions A,1988,19(9):2319-2331.
[6]徐炯,周一工.700℃高效超超临界技术的发展[J].中外能源,2012,17(6):13-17.
[7]Viswanathan R,Coleman K,Rao U.Materials for ultra-supercritical coal-fired pow er plant boilers[J].International Journal of Pressure Vessels and Piping,2006,83(11-12):778-783.
[8]梅声勇,郑磊,蒙肇斌,等.GH105合金铸锭元素偏析和均匀化工艺[J].北京科技大学学报,2009,31(6):714-718.
[9]贾鹏,王恩刚,鲁辉,等.电磁场对Inconel 625合金凝固组织及力学性能的影响[J].金属学报,2013,49(12):1573-1580.
[10]Rozmus-Górnikowska M,Blicharski M.Microsegregation and Precipitates in Inconel 625 Arc Weld Overlay Coatings on Boiler Pipes/M ikrosegregacja I Wydzielenia W Pow lokach Ze Stopu Inconel 625 Napaw anych Lukow o Na Rury Kotlow e[J].Archives of M etallurgy and M aterials,2015,60(4):2599–2606.
[11]Kearsey R M,Beddoes J C,Jones P,et al.Compositional design considerations for microsegregation in single crystal superalloy systems[J].Intermetallics,2004,12(7-9):903-910.
[12]郭建亭.高温合金材料学[M].下册.北京:科学出版社,2008:36-58.
[13]Dupont J N,Notis M R,Marder A R,et al.Solidification of Nb-bearing superalloys:Part I.Reaction sequences[J].M etallurgical and M aterials Transactions,1998,29(11):2785-2796.
[14]方姣,刘琛仄,刘军,等.粉末冶金高温合金差热曲线的相变温度分析方法[J].中国有色金属学报,2015,25(12):3352-3360.
[15]郭建亭.高温合金材料学[M].中册.北京:科学出版社,2008:357-384.
[16]胥国华,焦兰英,张北江,等.固溶冷却速度对GH4586合金组织及850℃拉伸性能的影响[J].材料热处理学报,2006,27(2):47-49.
[17]刘林,傅恒志,史正兴.凝固参数对定向镍基铸造高温合金中MC碳化物生长特性的影响[J].航空学报,1986,7(2):181-186.
[18]刘林,傅恒志,史正兴.高温合金中碳化物的初生形貌与晶体结构的关系[J].金属学报,1989,25(4):48-53.
[19]万华明,刘林,田荫棠,等.多面体晶体从金属熔体中生长的形态分析[J].西北工业大学学报,1992,10(3):318-322.
[20]卜凡征,王学敏,陈琳,等.Ti-Nb-Mo微合金钢回火过程中纳米碳化物的析出行为及组织演变[J].材料热处理学报,2015,36(8):96-103.
[21]李亚敏.Co、Zr、Cu在K4169合金中作用的研究[D].兰州:兰州理工大学,2011.