Microstructure and tensile properties of DD32 single crystal Ni-base superalloy repaired by laser metal forming
来源期刊：JOURNAL OF MATERIALS SCIENCE TECHNOLOG2020年第10期
论文作者：Shiwei Ci Jingjing Liang Jinguo Li Yizhou Zhou Xiaofeng Sun
文章页码：23 - 34
摘 要：In this work, the microstructure and tensile properties of DD32 single-crystal（SC） superalloy repaired by laser metal forming（LMF） using pulsed laser have been studied in detail. The microstructures of the deposited samples and the tensile-ruptured samples were characterized by optical microscopy（OM）,transmission electron microscope（TEM） and scanning electron microscope（SEM）. Due to high cooling rate, the primary dendrite spacing in the deposited area（17.2 μm） was apparently smaller than that in the substrate area（307 μm）, and the carbides in the deposited samples were also smaller compared with that in the substrate area. The formation of（γ + γ’） eutectic in the initial layer of repaired SC was inhibited because of the high cooling rate. As the deposition proceeded, the cooling rate decreased, and the（γ + γ’） eutectic increased gradually. The（γ + γ’） eutectic at heat-affected zone（HAZ） in the molten pool dissolved partly because of the high temperature at HAZ, but there were still residual eutectics. Tensile test results showed that tensile behavior of repaired SC at different temperatures was closely related to the MC carbides, solidification porosity, γ’ phase, and（γ + γ’） eutectic. At moderate temperature, the samples tested fractured preferentially at the substrate area due to the fragmentation of the coarse MC carbide in the substrate area. At elevated temperature, the（γ + γ’） eutectic and solidification porosity in the deposited area became the source of cracks, which deteriorated the high-temperature properties and made the samples rupture at the deposited area preferentially.
Shiwei Ci1,2，Jingjing Liang1,3,4，Jinguo Li1,4，Yizhou Zhou1，Xiaofeng Sun1
1. Institute of Metal Research, Chinese Academy of Sciences2. School of Materials Science and Engineering, University of Science and Technology of China3. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University
摘 要：In this work, the microstructure and tensile properties of DD32 single-crystal（SC） superalloy repaired by laser metal forming（LMF） using pulsed laser have been studied in detail. The microstructures of the deposited samples and the tensile-ruptured samples were characterized by optical microscopy（OM）,transmission electron microscope（TEM） and scanning electron microscope（SEM）. Due to high cooling rate, the primary dendrite spacing in the deposited area（17.2 μm） was apparently smaller than that in the substrate area（307 μm）, and the carbides in the deposited samples were also smaller compared with that in the substrate area. The formation of（γ + γ’） eutectic in the initial layer of repaired SC was inhibited because of the high cooling rate. As the deposition proceeded, the cooling rate decreased, and the（γ + γ’） eutectic increased gradually. The（γ + γ’） eutectic at heat-affected zone（HAZ） in the molten pool dissolved partly because of the high temperature at HAZ, but there were still residual eutectics. Tensile test results showed that tensile behavior of repaired SC at different temperatures was closely related to the MC carbides, solidification porosity, γ’ phase, and（γ + γ’） eutectic. At moderate temperature, the samples tested fractured preferentially at the substrate area due to the fragmentation of the coarse MC carbide in the substrate area. At elevated temperature, the（γ + γ’） eutectic and solidification porosity in the deposited area became the source of cracks, which deteriorated the high-temperature properties and made the samples rupture at the deposited area preferentially.
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