| LIU Fen-cheng,REN Hang,WANG Xiao-guang,LYU Fei-yue.Dendritic Segregation of Nb Modified GH4169 Superalloy Fabricated by Laser Additive Manufacturing[J],48(5):123-131 |
| Dendritic Segregation of Nb Modified GH4169 Superalloy Fabricated by Laser Additive Manufacturing |
| Received:December 24, 2018 Revised:May 20, 2019 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2019.05.019 |
| KeyWord:GH4169 nickel based superalloy laser additive manufacturing alloying dendritic segregation heat treatment |
| Author | Institution |
| LIU Fen-cheng |
National Defense Key Discipline Laboratory of Light Alloy Processing Science and Technology, Nanchang Hangkong University, Nanchang , China |
| REN Hang |
National Defense Key Discipline Laboratory of Light Alloy Processing Science and Technology, Nanchang Hangkong University, Nanchang , China |
| WANG Xiao-guang |
National Defense Key Discipline Laboratory of Light Alloy Processing Science and Technology, Nanchang Hangkong University, Nanchang , China |
| LYU Fei-yue |
National Defense Key Discipline Laboratory of Light Alloy Processing Science and Technology, Nanchang Hangkong University, Nanchang , China |
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| Abstract: |
| The work aims to alleviate dendritic segregation of Nb modified GH4169 superalloy fabricated by laser additive manufacturing (LAM) after different heat treatments. Nb powders were added to the original GH4169 superalloy powder by ball milling, and the alloying GH4169 samples with high Nb content were fabricated by LAM. The as-deposited, solid solution and direct aging (DA) samples were analyzed by optical microscopy (OM), scanning electron microscopy (SEM), energy spectrum analysis (EDS) and Vickers hardness test. The effects of dendritic segregation caused by Nb content in LAM alloying GH4169 superalloy on microstructure and microhardness of as-deposited and heat treated sample were studied. On the one hand, the ad-dition of Nb made the dendrite structure more obvious, and promoted the precipitation of γ+Laves interdendritic eutectics, and the morphology of γ+Laves interdendritic eutectics was gradually like net. With the increase of Nb content in LAM alloying GH4169 superalloy, the hardness value could reach 534.1HV from 228.4HV. On the other hand, the content of Nb in the dendrite core increased and the differences between dendrite core and interdendrite decreased, which made the segregation ratio decreased from 8.59 to 4.13. After solution treatment, the dendrite structure characteristics of the sample disappeared obviously with the rise of heat treatment temperature. The quantity of Laves phase between dendrites decreased and the microhardness value decreased because of the different degree dissolution of the Laves phase, showing the alleviation of dendritic segregation of LAM alloying GH4169 superalloy. The decreasing trend gradually dwindled with the increase of solution temperature. With the increase of Nb content, the microhardness uniformity of samples after aging treatment was improved and the difference of precipitation of strengthening phases in dendritic structure reduced. Suitable heat treatment can not only make alloying elements homogenized, but also reduce the difference of precipitation of strengthening phases in dendritic structure, and alleviate the dendritic segregation in LAM alloying GH4169 superalloy. |
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