Fundamental Study on the Development of Pure Magnesium Parts by Additive Manufacturing: An Experimental and Computational Analysis

Kyeong‑Min Kim; Uijong Lee; Hyungsoo Lee; Seong‑Moon Seo; Eun‑Joon Chun

doi:10.1007/s12540-022-01250-4

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자료유형: 학술저널

저자정보: Kyeong‑Min Kim (Pukyong National University) Uijong Lee (Doosan Heavy Industries and Construction) Hyungsoo Lee (Korea Institute of Materials Science) Seong‑Moon Seo (Korea Institute of Materials Science) Eun‑Joon Chun (Pukyong National University)

저널정보: 대한금속·재료학회 Metals and Materials International Metals and Materials International Vol.29 No.3

발행연도: 2023.3

수록면: 777 - 794 (18page)

DOI: 10.1007/s12540-022-01250-4

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CM247LC, a Ni-based superalloy, is employed in the high-temperature components of gas turbines, such as the blades.However, the welds of CM247LC are highly susceptible to various types of cracking, thereby limiting the applicability ofthis superalloy. To overcome this critical limitation, in this paper, we propose a novel Varestraint test procedure for evaluatingthe susceptibility of oscillated CM247LC welds to solidification cracking. By visualizing the temperature in real timeduring testing, we quantitatively evaluate changes in the susceptibility of CM247LC to solidification cracking owing to arcoscillation. The solidification cracking temperature range (SCTR) for the CM247LC alloy is 400 K in the case of linear welding,whereas it is 275 and 475 K in the case of oscillation welding at frequencies of 0.6 and 1.2 Hz, respectively. Notably,the SCTR narrows or widens depending on the oscillation conditions. By contrast, almost no changes in the mushy zonerange are theoretically calculated via the diffusion-controlled Scheil equation. This result suggests that the SCTR must beclosely examined according to the oscillation conditions in the welding-based manufacturing of gas turbine blades fromCM247LC. The mechanism underlying the reduction in the SCTR under oscillation welding (0.6 Hz) is clarified based onthe relationship between the solidification microstructure in the crack path and propagation behavior of the solidificationcrack. This mechanism is also explained by the equiaxed dendritic subgrain structure, the formation of which is attributedto the lower ratio between the obtained temperature gradient (G) and the sonification rate (R), i.e., G/R (47.26 K∙s/mm2)of the oscillated welds compared with those of the linear welds (146.34 K∙s/mm2), which enhances the crack propagationresistance. Furthermore, solidification grain refinement, which also could have enhanced the solidification crack propagationresistance, is detected.

#Gas turbine blade · CM247LC superalloy · Arc oscillation welding · Solidification cracking susceptibility · Varestraint test

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