钴基高温合金GH5605铸态组织及高温扩散退火过程中元素再分配
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摘要
利用光学显微镜(OM)、场发射扫描电子显微镜(FESEM)、能谱分析(EDS)并结合热力学及动力学计算结果对采用真空感应熔炼和电渣重熔二联工艺生产的GH5605合金电渣锭的枝晶形貌、元素偏析和析出相进行分析.探索了合金的高温扩散退火制度并结合差示扫描量热仪(DSC)和热压缩模拟实验分析高温扩散退火前后的合金特征.结果表明:GH5605合金中的枝晶和元素偏析情况较轻,主要偏析元素是Cr和W并在枝晶间处偏聚,电渣锭中的主要析出相包括奥氏体、晶界M23C6以及晶内和晶界处的奥氏体与M23C6板条状共晶相.经1210℃/8 h扩散退火处理后枝晶和元素偏析基本消除,共晶相基本回溶.
The dendritic morphology,elements segregation index,precipitates morphology,and precipitates types in GH5605 ingot produced by vacuum induction melting and electroslag remelting were investigated by using optical microscopy( OM),field-emission scanning electron microscopy( FESEM),energy-dispersive X-ray spectroscopy( EDS) spectrum analysis and the results of thermodynamic and kinetic calculations by Thermal-Calc and JMatPro sofeware. To study the effects of high-temperature diffusion annealing on GH5605 ingot,the annealing system was investigated and the microstructure and macrostructure characteristics of GH5605 ingot were analyzed before and after the diffusion annealing by differential scanning calorimetry( DSC) and thermal compression simulation tests in Gleeble 3800 test machine. In the OM results,dendrites are not obvious,and secondary dendritic arms cannot be distinguished in the GH5605 surface but they are gradually clearer toward the center area. The EDS results show that element segregation index is comparably small in GH5605 ingot; every element segregation index is in the range of 0. 9-1. 4 which is not as large as those of nickelbased superalloy. The main segregating elements during solidification are Cr and W which mainly segregate in the dendritic regions.According to the FESEM results,the precipitate phases include austenite and grain boundary carbide M2 3 C6 and because of the Cr and W segregation at dendritic arms,an unexpected eutectic phase comprising austenite and M23 C6 appears,and the alternating lamellae of austentite and M23 C6 develop a lathlike morphology. Different macrostructure and microstructure characteristics including the morphology of dendritic,elements segregation index,grain size,morphology and the amount of eutectic phase were analyzed and compared in different annealing times. The high-temperature diffusion annealing system is optimal at 1210 ℃/8 h,at which the dendrites and elemental segregation are substantially eliminated,and the eutectic phase is almost dissolved.
The dendritic morphology,elements segregation index,precipitates morphology,and precipitates types in GH5605 ingot produced by vacuum induction melting and electroslag remelting were investigated by using optical microscopy( OM),field-emission scanning electron microscopy( FESEM),energy-dispersive X-ray spectroscopy( EDS) spectrum analysis and the results of thermodynamic and kinetic calculations by Thermal-Calc and JMatPro sofeware. To study the effects of high-temperature diffusion annealing on GH5605 ingot,the annealing system was investigated and the microstructure and macrostructure characteristics of GH5605 ingot were analyzed before and after the diffusion annealing by differential scanning calorimetry( DSC) and thermal compression simulation tests in Gleeble 3800 test machine. In the OM results,dendrites are not obvious,and secondary dendritic arms cannot be distinguished in the GH5605 surface but they are gradually clearer toward the center area. The EDS results show that element segregation index is comparably small in GH5605 ingot; every element segregation index is in the range of 0. 9-1. 4 which is not as large as those of nickelbased superalloy. The main segregating elements during solidification are Cr and W which mainly segregate in the dendritic regions.According to the FESEM results,the precipitate phases include austenite and grain boundary carbide M2 3 C6 and because of the Cr and W segregation at dendritic arms,an unexpected eutectic phase comprising austenite and M23 C6 appears,and the alternating lamellae of austentite and M23 C6 develop a lathlike morphology. Different macrostructure and microstructure characteristics including the morphology of dendritic,elements segregation index,grain size,morphology and the amount of eutectic phase were analyzed and compared in different annealing times. The high-temperature diffusion annealing system is optimal at 1210 ℃/8 h,at which the dendrites and elemental segregation are substantially eliminated,and the eutectic phase is almost dissolved.
引文
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[17] Vacchieri E,Costa A,Roncallo G,et al. Service induced fcc→hcp martensitic transformation in a Co-based superalloy. Mater Sci Technol,2017,33(9):1100
[18] Koizumi Y,Suzuki S,Yamanaka K,et al. Strain-induced martensitic transformation near twin boundaries in a biomedical Co--Cr-Mo alloy with negative stacking fault energy. Acta Mater,2013,61(5):1648
[19] Bensona M L,Liaw P K,Saleh T A,et al. Deformation-induced phase development in a cobalt-based superalloy during monotonic and cyclic deformation. Phys B,2006,385-386:523
[20] Tawancy H M,Ishwar V R,Lewis B E. On the fcc-hcp transformation in a cobalt-base superalloy(Haynes alloy No. 25). J Mater Sci Lett,1986,5:337
[21] Saldivar G,Mani M,Salinas R,et al. Effect of solution treatments on the fcc/hcp isothermal martensitic transformation in Co--27Cr-5Mo-0. 05C aged at 800℃. Scripta Mater,1999,40(6):717
[22] Jiang H,Dong J X,Zhang M C,et al. Microstructure and homogenization of as-cast 617B alloy for 700℃ultra-supercritical boilers. J Univ Sci Technol Beijing,2014,36(6):795(江河,董建新,张麦仓,等. 700℃超超临界锅炉材料617B合金铸态组织及均匀化工艺.北京科技大学学报,2014,36(6):795)
[2] Keyvani M,Garcin T,Fabrègue D,et al. Continuous measurements of recrystallization and grain growth in cobalt super alloys.Metall Mater Trans A,2017,48(5):2363
[3] Favre J,Koizumi Y,Chiba A,et al. Deformation behavior and dynamic recrystallization of biomedical Co-Cr--W-Ni(L--605)alloy. Metall Mater Trans A,2013,44(6):2819
[4] Kumar V A,Gupta R K,Murty S V S N,et al. Hot workability and microstructure control in Co20Cr15W10Ni cobalt based superalloy. J Alloys Compd,2016,676:527
[5] Ueki K,Ueda K,Narushima T. Microstructure and mechanical properties of heat-treated Co--20Cr--15W--10Ni alloy for biomedical application. Metall Mater Trans A,2016,47(6):2773
[6] Yamanaka K,Mori M,Kuramoto K,et al. Development of new Co-Cr-W-based biomedical alloys:effects of microalloying and thermomechanical processing on microstructures and mechanical properties. Mater Des,2014,55:987
[7] Academic Committee of the Superalloys,CSM. China Superalloys Handbooks(volume 1). Beijing:Standard Press of China,2012(中国金属学会高温材料分会.中国高温合金手册(上卷).北京:中国标准出版社,2012)
[8] Gui W M,Zhang H Y,Yang M,et al. Influence of type and morphology of carbides on stress-rupture behavior of a cast cobalt-base superalloy. J Alloys Compd,2017,728:145
[9] Gui W M,Zhang H Y,Yang M,et al. The investigation of carbides evolution in a cobalt-base superalloy at elevated temperature.J Alloys Compd,2017,695:1271
[10] Koβmann J,Zenk C H,Lopez-Galilea I,et al. Microsegregation and precipitates of an as-cast Co-based superalloy—microstructural characterization and phase stability modelling. J Mate Sci,2015,50(19):6329
[11] Chiba A,Kurosu S,Akasaka Y,et al. Co-based Alloy for Living Body and Stent:United States Patent,20130226281A1. 2013-8-29
[12] Magyar S T,Hirakis E C,Gell M L,et al. Oxidation Resistant Cobalt Base Alloy:United States Patent,US4078922A. 1978-3-14
[13] Favre J,Fabrègue D,Maire E,et al. Grain growth and static recrystallization kinetics in Co--20Cr--15W--10Ni(L--605)cobaltbase superalloy. Philos Mag,2014,94(18):1992
[14] Favre J,Fabrègue D,Yamanaka K,et al. Modeling dynamic recrystallization of L--605 cobalt superalloy. Mater Sci Eng A,2016,653:84
[15] Weeton J W,Signorelli R A. An Investigation of Lamellar Structures and Minor Phase in Eleven Cobalt-Base Alloys Before and After Heat Treatment. Washington,1954
[16] Mani A,Salinas R,Lopez H F. Deformation induced FCC to HCP transformation in a Co-27Cr--5Mo--0. 05C alloy. Mater Sci Eng A,2011,528(7-8):3037
[17] Vacchieri E,Costa A,Roncallo G,et al. Service induced fcc→hcp martensitic transformation in a Co-based superalloy. Mater Sci Technol,2017,33(9):1100
[18] Koizumi Y,Suzuki S,Yamanaka K,et al. Strain-induced martensitic transformation near twin boundaries in a biomedical Co--Cr-Mo alloy with negative stacking fault energy. Acta Mater,2013,61(5):1648
[19] Bensona M L,Liaw P K,Saleh T A,et al. Deformation-induced phase development in a cobalt-based superalloy during monotonic and cyclic deformation. Phys B,2006,385-386:523
[20] Tawancy H M,Ishwar V R,Lewis B E. On the fcc-hcp transformation in a cobalt-base superalloy(Haynes alloy No. 25). J Mater Sci Lett,1986,5:337
[21] Saldivar G,Mani M,Salinas R,et al. Effect of solution treatments on the fcc/hcp isothermal martensitic transformation in Co--27Cr-5Mo-0. 05C aged at 800℃. Scripta Mater,1999,40(6):717
[22] Jiang H,Dong J X,Zhang M C,et al. Microstructure and homogenization of as-cast 617B alloy for 700℃ultra-supercritical boilers. J Univ Sci Technol Beijing,2014,36(6):795(江河,董建新,张麦仓,等. 700℃超超临界锅炉材料617B合金铸态组织及均匀化工艺.北京科技大学学报,2014,36(6):795)
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