Tensile and creep resistance improvement of GH4975 alloy for turbine discs via electron beam smelting layer solidification technology

Materials Science and Engineering: A(2024)

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Abstract
A difficult-to-deform superalloy for turbine disks, which can be used at 850 °C for a long time, was prepared by electron beam melting layer solidification (EBSL) technology with high purity and fine structure. Subsequently, the ingot was processed by hot extrusion technology instead of conventional hot forging, and then the tensile and creep tests were performed after standard heat treatment. The results show that the EBSL alloy exhibits excellent high-temperature strength and creep rupture life compared to the conventional preparation method. Among them, the yield strengths at 20°C and 850°C are 8.1% and 5.2% higher than those in the literature, and the creep rupture life at 850°C and 412 MPa is 1.53 times higher than that in the literature. The dislocation-precipitate interaction reveals that dislocation shearing γ' phase is the major mechanism at 20°C and 850°C tensile, and Orowan looping and stacking fault shearing are the decisive mechanism during creep at 850°C and 412 MPa. MC carbides remaining during solidification are the main source of cracks during deformation by fracture analysis. The reasons for refining the microstructure and improving the purity by electron beam melting are analyzed and explained. We believe this work can provide new ideas and methods for preparing superalloys.
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