The influence of grain boundary angle on the hot cracking of single crystal superalloy DD6

Peng, Rong; Wang, N.; Wang, L.; Yang, Rumei; Yao, Wei

doi:10.1016/j.jallcom.2016.03.164

Cited by 40 publications

(13 citation statements)

References 15 publications

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“…~100 boundaries over the region of interest were analyzed and classified based on their misorientation angle and their cracking susceptibility, as reported inFigure 6b, which suggests that high angle grain boundaries (HAGB, misorientation > 15°) are sensitive to cracking whereas the low angle grain boundaries (LAGB, misorientation < 15°) remain uncracked. This result is consistent with the literature dealing with welding and casting of non-weldable nickel-base superalloys[1,2,35].…”

supporting

confidence: 93%

Hot cracking mechanism affecting a non-weldable Ni-based superalloy produced by selective electron Beam Melting

et al. 2018

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A non weldable nickel-based superalloy was fabricated by powder bed-based selective electron beam melting (S-EBM). The as-built samples exhibit a heterogeneous microstructure along the build direction. A gradient of columnar grain size as well as a significant gradient in the γ' precipitate size were found along the build direction. Microstructural defects such as gas porosity inherited from the powders, shrinkage pores and cracks inherited from the S-EBM process were identified. The origins of those defects are discussed with a particular emphasis on crack formation. Cracks were consistently found to propagate intergranular and the effect of crystallographic misorientation on the cracking behavior was investigated. A clear correlation was identified between cracks and high angle grain boundaries (HAGB). The cracks were classified as hot cracks based on the observation of the fracture surface of microtensile specimens machined from as-built S-EBM samples. The conditions required to trigger hot cracking, namely, presence of a liquid film during the last stage of solidification and thermal stresses are discussed within the framework of additive manufacturing. Understanding the cracking mechanism enables to provide guidelines to obtain crack-free specimens of non-weldable Ni-based superalloys produced by S-EBM.

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supporting

confidence: 93%

Hot cracking mechanism affecting a non-weldable Ni-based superalloy produced by selective electron Beam Melting

et al. 2018

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“…Similar observations are also available in [13,23] and in shipbuilding engineering. This prediction is also in agreement with the observation derived from PFM that as the grain boundary angle to the weld centerline increases, the susceptibility to solidification cracking increases [33]. The weld's transverse stress component is therefore proven to contribute to the longitudinally centerline-oriented appearance of the solidification crack.…”

Section: Methodssupporting

confidence: 90%

Solidification Crack Evolution in High-Strength Steel Welding Using the Extended Finite Element Method

2020

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High-strength steel suffers from an increasing susceptibility to solidification cracking in welding due to increasing carbon equivalents. However, the cracking mechanism is not fully clear for a confidently completely crack-free welding process. To present a full, direct knowledge of fracture behavior in high-strength steel welding, a three-dimensional (3-D) modeling method is developed using the extended finite element method (XFEM). The XFEM model and fracture loads are linked with the full model and the output of the thermo-mechanical finite element method (TM-FEM), respectively. Solidification cracks in welds are predicted to initiate at the upper tip at the current cross-section, propagate upward to and then through the upper weld surface, thereby propagating the lower crack tip down to the bottom until the final failure. This behavior indicates that solidification cracking is preferred on the upper weld surface, which has higher weld stress introduced by thermal contraction and solidification shrinkage. The modeling results show good agreement with the solidification crack fractography and in situ observations. Further XFEM results show that the initial defects that exhibit higher susceptibility to solidification cracking are those that are vertical to the weld plate plane, open to the current cross-section and concentratedly distributed compared to tilted, closed and dispersedly distributed ones, respectively.

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“…After a series of experiments, it is found that the grain boundary is likely to crack if the misorientation angle exceeded a critical value θ c , which is dependent on temperature and chemical composition. Wang et al [40] proposed that the θ c was 13°, while the values such as 15°and 16°were also reported by Chauvet et al [35] and Rong et al [41], respectively. The uncracked grain boundary misorientation (17°) is close to the reported values, thus it is not easy to tell if the uncracked grain boundary is a high angle grain boundary.…”

Section: Grain Boundary Characteristics To Crack Susceptibilitymentioning

confidence: 71%

Mechanism of heat affected zone cracking in Ni-based superalloy DZ125L fabricated by laser 3D printing technique

Chen

Tamura

2018

Materials & Design

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• The heat affected zone cracking initiates due to the re-melting of preexisting intergranular γ/γ′ eutectics and coarse γ′.• The transverse tensile strain/stress causing the initiation and propagation of crack is quantitatively measured.• The micro-size MC carbides are considered to be a possible contributor to the hot cracking initiation. Laser 3D printing is a promising technique to repair damaged Ni-based superalloy components. However, the occurrence of heat affected zone (HAZ) cracking severely limits its applicability. Here we unravel the cracking mechanism by studying the element, phase, defect, and strain distribution around an intergranular crack that initiated from the primary HAZ. Using synchrotron X-ray Laue microdiffraction, we measured high tensile strain/ stress transverse to the building direction in both the primary HAZ and the cladding layers, as well as highdensity dislocations, which resulted from the thermal contraction and rapid precipitation of γ′ phase. The crack initiated because the transverse tensile strain/stress tore up the liquid film formed by the low-melting point preexisting phases in the primary HAZ, such as γ/γ′ eutectics and coarse γ′ precipitates. The incoherent carbide particles were frequently observed near the crack root as local strain concentrators. In the cladding layers, micro-segregation could not be completely avoided, thus the hot crack continued to propagate over several layers with the assistance of the transverse tensile stress. Our investigations provide a useful guideline for the optimization of the 3D printing process to repair Ni-based superalloys with high susceptibility to hot cracking.

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The influence of grain boundary angle on the hot cracking of single crystal superalloy DD6

Cited by 40 publications

References 15 publications

Hot cracking mechanism affecting a non-weldable Ni-based superalloy produced by selective electron Beam Melting

Hot cracking mechanism affecting a non-weldable Ni-based superalloy produced by selective electron Beam Melting

Solidification Crack Evolution in High-Strength Steel Welding Using the Extended Finite Element Method

Mechanism of heat affected zone cracking in Ni-based superalloy DZ125L fabricated by laser 3D printing technique

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