Microstructure evolution and nucleation mechanism of Inconel 601H alloy welds by vibration-assisted GTAW
- 70 Downloads
Nickel-based alloys exhibit excellent high-temperature strength and oxidation resistance; however, because of coarse grains and severe segregation in their welding joints, these alloys exhibit increased susceptibility to hot cracking. In this paper, to improve the hot-cracking resistance and mechanical properties of nickel-based alloy welded joints, sodium thiosulfate was used to simulate crystallization, enabling the nucleation mechanism under mechanical vibration to be investigated. On the basis of the results, the grain refinement mechanism during the gas tungsten arc welding (GTAW) of Inconel 601H alloy under various vibration modes and parameters was investigated. Compared with the GTAW process, the low-frequency mechanical vibration processes resulted in substantial grain refinement effects in the welds; thus, a higher hardness distribution was also achieved under the vibration conditions. In addition, the γ' phase exhibited a dispersed distribution and segregation was improved in the welded joints with vibration assistance. The results demonstrated that the generation of free crystals caused by vibration in the nucleation stage was the main mechanism of grain refinement. Also, fine equiaxed grains and a dispersed γ' phase were found to improve the grain-boundary strength and reduce the segregation, contributing to preventing the initiation of welding hot cracking in nickel-based alloys.
Keywordsmechanical vibration nickel-based alloy grain refinement microstructure hot cracking
Unable to display preview. Download preview PDF.
The authors gratefully acknowledge the financial supported by the Natural Science Foundation of Hebei Province, China (No. E2017202011).
- J.C. Lippold, S.D Kiser, and J.N. Dupont, Welding Metallurgy and Weldability of Nickel-Base Alloys, John Wiley & Sons, New Jersey, 2009, p. 100.Google Scholar
- S.P. Tewari and A. Shanker, Effects of longitudinal vibration on tensile properties of weldments, Weld. J., 73(1994), 11, p. 272.Google Scholar
- S. Kou and Y. Le, Improving weld quality by low frequency arc oscillation, Weld. J., 1985, p. 51.Google Scholar
- J.R. Welty, C.E. Wicks, R.E. Wilson, and G.L. Rorrer, Fundamentals of Momentum, Heat, and Mass Transfer, 5th Ed., John Wiley & Sons, New Jersey, 2007, p. 144.Google Scholar
- L.X. Zhuang, X.Y. Yin, and H.Y. Ma, Fluid Mechanics, University of Science and Technology of China Press, HeFei, 1991, p. 321.Google Scholar
- H. Schlichting and K. Gersten, Boundary-Layer Theory, McGraw-Hill Book Company, New York, 1979, p. 24.Google Scholar
- S. Kou, Welding Metallurgy, 2nd Ed., John Wiley & Sons, New Jersey, 2003, p. 170.Google Scholar
- S.S. Ao, Zhen Luo, P. Shan, and W.D. Liu, Microstructure of inconel 601 nickel-based superalloy laser welded joint, Chin. J. Nonferrous Met., 25(2015), 8, p. 2099.Google Scholar