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 sampl...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(17.2μm)was apparently smaller than that in the substrate area(307μm),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.展开更多
基金the National Key R&D Program of China(No.2018YFB1106600),the National Key R&D Program of China(Nos.2017YFA0700703 and 2018YFB1106000)the National Natural Science Foundation of China(NSFC)(Nos.51771190,51671189,U1508213)+1 种基金the National High Technology Research and Development Program(“863”)(No.2014AA041701)the Fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP201834)。
文摘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(17.2μm)was apparently smaller than that in the substrate area(307μm),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.
