Liquation Cracking in the Heat-Affected Zone of IN738 Superalloy Weld

Chen, Kai-Cheng; Chen, Tai-Cheng; Shiue, Ren-Kae; Tsay, L.W.

doi:10.3390/met8060387

Cited by 40 publications

(14 citation statements)

References 44 publications

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“…Previous research works have thoroughly investigated the influence of chemical composition and microstructure resulting from different thermal treatments on the hot cracking susceptibility of alloy 718 [9,[14][15][16][17][18] and alloy 738 [19]. This has led to contradictory conclusions about the influence of grain size on the hot cracking susceptibility of alloy 718 castings.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Hot Cracking Susceptibility of TIG and Laser Beam Welded Alloy 718 by Varestraint Testing

Álvarez

Vázquez

Ruiz

et al. 2019

Metals

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Reduced hot cracking susceptibility is essential to ensure the flawless manufacturing of nickel superalloys typically employed in welded aircraft engine structures. The hot cracking of precipitation strengthened alloy 718 mainly depends on chemical composition and microstructure resulting from the thermal story. Alloy 718 is usually welded in a solution annealed state. However, even with this thermal treatment, cracks can be induced during standard industrial manufacturing conditions, leading to costly and time-consuming reworking. In this work, the cracking susceptibility of wrought and investment casting alloy 718 is studied by the Varestraint test. The test is performed while applying different welding conditions, i.e., continuous tungsten inert gas (TIG), low frequency pulsed TIG, continuous laser beam welding (LBW) and pulsed LBW. Welding parameters are selected for each welding technology in order to meet the welding quality criteria requested for targeted aeronautical applications, that is, full penetration, minimum cross-sectional welding width and reduced overhang and underfill. Results show that the hot cracking susceptibility of LBW samples determined by the Varestraint test is enhanced due to extended center line hot cracking, resulting in a fish-bone like cracking pattern. On the contrary, the minor effect of material source (wrought or casting), grain size and pulsation is observed. In fact, casting samples with a 30 times coarser grain size have shown better performance than wrought material.

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Section: Introductionmentioning

confidence: 99%

Comparison of Hot Cracking Susceptibility of TIG and Laser Beam Welded Alloy 718 by Varestraint Testing

Álvarez

Vázquez

Ruiz

et al. 2019

Metals

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“…Since these alloys are not optimized for additive manufacturing, processing is challenging. Specifically, the high amount of γ’ precipitates (up to 80 vol.%) and the strong tendency for segregation lead to a high susceptibility for cracks including solidification cracking [ 16 ], liquation cracking [ 17 ] or strain age cracking [ 18 , 19 ]. Recent studies have shown that apart from alloy modifications [ 20 , 21 , 22 ], either a high amount of high angle grain boundaries or no high angle grain boundaries at all (single crystalline, SX) are necessary to process these alloys without cracks [ 8 , 23 ].…”

Section: Introductionmentioning

confidence: 99%

A Single Crystal Process Window for Electron Beam Powder Bed Fusion Additive Manufacturing of a CMSX-4 Type Ni-Based Superalloy

2021

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Using suitable scanning strategies, even single crystals can emerge from powder during additive manufacturing. In this paper, a full microstructure map for additive manufacturing of technical single crystals is presented using the conventional single crystal Ni-based superalloy CMSX-4. The correlation between process parameters, melt pool size and shape, as well as single crystal fraction, is investigated through a high number of experiments supported by numerical simulations. Based on these results, a strategy for the fabrication of high fraction single crystals in powder bed fusion additive manufacturing is deduced.

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“…Preheating is usually recommended by the welding community to limit thermal gradients (K/m) during cooling, thus improving the material's resistance to hot cracking. [12] Preheating temperature and time, i.e., the influence of short-term heat treatment cycles on nickel superalloy's microstructure changes, is a particularly important area in designing new technologies, as welding processes are widely used for regenerating foundry defects and repairing of serviced components. [13][14][15][16] Hot cracking, including liquation cracking in the heat-affected zone, is directly dependent on the c¢ behavior during heating and subsequent cooling.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the γ′ Precipitates Dissolution in a Ni-Based Superalloy During Stress-Free Short-Term Annealing at High Homologous Temperatures

Rakoczy

Grudzień-Rakoczy

Hanning

et al. 2021

Metall Mater Trans A

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The equiaxed Ni-based superalloy René 108 was subjected to short-term annealing at five temperatures between 900 °C and 1100 °C. The phase composition, phase lattice parameters, microstructure, stereological parameters, and chemical composition of γ′ precipitates were investigated by thermodynamic simulations, X-ray diffraction, scanning and transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Analysis of the γ and γ′ lattice parameters using the Nelson-Riley extrapolation function showed that the misfit parameter for temperatures 900 °C to 1050 °C is positive (decreasing from 0.32 to 0.11 pct). At 1100 °C, the parameter becomes negative, δ = − 0.18 pct. During the short-term annealing, γ′ precipitates dissolution occurred progressing more rapidly with increasing temperatures. The surface fraction of γ′ precipitates decreased with increasing temperature from 0.52 to 0.34. The dissolution of γ′ precipitates did not only proceed through uninterrupted thinning of each individual precipitate, but also included more complex mechanisms, including splitting. Based on transmission electron microscopy, it was shown that after γ′ precipitates dissolution, the matrix close to the γ/γ′ interface is strongly enriched in Co and Cr and depleted in Al.

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Liquation Cracking in the Heat-Affected Zone of IN738 Superalloy Weld

Cited by 40 publications

References 44 publications

Comparison of Hot Cracking Susceptibility of TIG and Laser Beam Welded Alloy 718 by Varestraint Testing

Comparison of Hot Cracking Susceptibility of TIG and Laser Beam Welded Alloy 718 by Varestraint Testing

A Single Crystal Process Window for Electron Beam Powder Bed Fusion Additive Manufacturing of a CMSX-4 Type Ni-Based Superalloy

Investigation of the γ′ Precipitates Dissolution in a Ni-Based Superalloy During Stress-Free Short-Term Annealing at High Homologous Temperatures

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