Electron Beam Welding of Nimonic 80A Superalloy: Microstructure Evolution and EBSD Study After Aging Heat Treatment
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The purpose of this research was to evaluate integrity and microstructure changes of the electron beam-welded Nimonic 80A and the base metal after aging heat treatment process, i.e., 700 °C/72 h/air cooling. Here, microstructure, microhardness and tensile were investigated by various tools, i.e., scanning electron microscope with energy-dispersive spectroscopy and electron backscatter diffraction, x-ray diffraction analysis and Vickers hardness. Evaluation of microstructure shows that the weld zone mainly consists of columnar dendrites. The effect of aging heat treatment on the microstructure morphology and phase structure is very limited. Also, it was observed that there are obvious segregation and precipitates in intracrystalline and along the grain boundaries after aging heat treatment. Electron backscatter diffraction results show that the weld zone and base metal have a clear difference in the grain boundary characterization and kernel average misorientation at room temperature and after aging heat treatment, which leads to a difference in microhardness of the weld zone. In addition, the relationship between microhardness and tensile strength is discussed.
Keywordsaging heat treatment electron backscatter diffraction electron beam welding heat source model Nimonic 80A the finite element method
This work was supported by the National Natural Science Research Foundation of China (11327801, 11502151, 11772209 and 11572057), the Program for Changjiang Scholars and Innovative Research Team (IRT14R37), the Key Science and Technology Support Program of Sichuan Province (2015JPT0001) and supported by the fund of State Key Laboratory of Long-life High Temperature Materials.
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