Effects of Grain Boundary Microconstituents on Heat-Affected Zone Cracks in a Mar-M004 Weldment

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

doi:10.3390/met8040201

Cited by 3 publications

(2 citation statements)

References 36 publications

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“…Furthermore, these boride particles decrease the solidus temperature at which non-equilibrium intergranular liquation is induced in the HAZ during the heating cycle of welding, thereby enhancing the cracking susceptibility of the weld [38]. In prior studies, the borides and intermetallics at the interdendritic boundaries are more likely to melt during repair-welding of Mar-M004 superalloy [39,40].…”

Section: Discussionmentioning

confidence: 98%

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

Chen

Shiue

et al. 2018

Metals

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Abstract:The main scope of this study investigated the occurrence of liquation cracking in the heat-affected zone (HAZ) of IN738 superalloy weld, IN738 is widely used in gas turbine blades in land-based power plants. Microstructural examinations showed considerable amounts of γ' uniformly precipitated in the γ matrix. Electron probe microanalysis (EPMA) maps showed the γ-γ' colonies were rich in Al and Ti, but lean in other alloy elements. Moreover, the metal carbides (MC), fine borides (M 3 B 2 and M 5 B 3 ), η-Ni 3 Ti, σ (Cr-Co) and lamellar Ni 7 Zr 2 intermetallic compounds could be found at the interdendritic boundaries. The fracture morphologies and the corresponding EPMA maps confirmed that the liquation cracking in the HAZ of the IN738 superalloy weld resulted from the presence of complex microconstituents at the interdendritic boundaries.

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Section: Discussionmentioning

confidence: 98%

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

Chen

Shiue

et al. 2018

Metals

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“…It is known that the Ni-based alloys are prone to hot cracking during welding [10][11][12][13][14][15]. The formation of low temperature liquid films and eutectic constituents at the solidified boundaries accounts for the occurrence of hot cracking of the Ni-based alloys [16,17].…”

Section: Introductionmentioning

confidence: 99%

The Comparison of Cracking Susceptibility of IN52M and IN52MSS Overlay Welds

Chen

et al. 2019

Metals

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Overlay-welding of IN52M and IN52MSS onto CF8A stainless steel (SS) was conducted by a gas tungsten arc welding process in multiple passes. An electron probe micro-analyzer (EPMA) was applied to determine the distributions and chemical compositions of the grain boundary microconstituents, and the structures were identified by electron backscatter diffraction (EBSD). The hot cracking of the overlay welds was related to the microconstituents at the interdendritic boundaries. The formation of γ-intermetallic (Ni 3 (Nb,Mo)) eutectics was responsible predominantly for the hot cracking of the 52M and 52MSS overlays. The greater Nb and Mo contents in the 52MSS overlay enhanced the formation of coarser microconstituents in greater amounts at the interdendritic boundaries. Thus, the hot cracking sensitivity of the 52MSS overlay was higher than that of the 52M overlay. Moreover, migrated grain boundaries were observed in the 52M and 52MSS overlays but did not induce ductility dip cracking (DDC) in this study. amount of interdendritic phases [25]. Coarse (Nb,Ti)C precipitates in 52M overlays will enhance the formation of Laves phases and increase their size [25,26], leading to increased hot crack sensitivity of the overlay welds.Besides the occurrence of hot cracking, Ni-based deposits for repair-welding of nuclear reactor components can be susceptible to ductility dip cracking (DDC) [27][28][29]. DDC in a Ni-based alloy weld mainly occurs in the reheated weld at elevated temperatures, and it is related to grain boundary (GB) sliding, impurity segregation at GBs, and intergranular precipitation [30]. GB sliding is responsible for the DDC of 52M deposits in strain-to-fracture tests [31]. Moreover, ductility dip cracks are initiated due to the combined effects of the strain concentration on the concave side of the grain boundary, the orientation of the GB to the loading direction, and GB disorientation [32]. In a prior study, IN52 alloy is reported to be more susceptible to DDC than IN82 alloy [33]. Adding Nb and Ti into IN52 alloy can reduce its DDC susceptibility due to the precipitation of NbC and TiC at the GBs [30]. It was reported that the DDC of a 52MSS weld, which was modified from 52M by adding 2.5% Nb and 3.0% Mo, can be alleviated even after multi-pass welding [34,35].In this study, IN52M and IN52MSS fillers were employed to perform overlay-welding on CF8A SS substrate. The microstructures and chemical compositions of the microconstituents at the solidified boundaries of the overlay welds were investigated. The hot cracking tendency and DDC of 52M and 52MSS overlays were evaluated by inspecting the interior microfissures carefully. Grain boundary micro-constituents were analyzed by electron backscatter diffraction (EBSD) to identify the complex phases. Furthermore, the relationships between microstructural features and the cracking tendencies of the overlay welds were correlated with those interdendritic precipitates.

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Microstructure and selected properties of the solution heat-treated MAR-M247 Ni-based superalloy fabricated via directional solidification

Rakoczy,

Grudzień-Rakoczy,

Cygan

et al. 2023

Int J Adv Manuf Technol

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This work focuses on MAR-M247 Ni-based superalloy manufactured via directional solidification at various withdrawal rates (3.4 or 5.0 mm/min) and shell mold temperatures (1510 °C or 1566 °C) after solution heat-treatment (SHT). Observations and analyses of four casting variants were carried out using thermodynamic simulations, differential scanning calorimetry (DSC), X-ray diffraction (XRD), light microscopy (LM), scanning electron microscopy (SEM), X-ray spectroscopy (EDX), and tensile tests at ambient temperature. The solidus and liquidus temperatures were very similar for all variants and were in the range of 1263–1264 °C and 1356–1359 °C, respectively. The presence of the γ, γ′, MC carbides, and M5B3 phases was confirmed. Microstructure differences were observed depending on the manufacturing parameters. The castings’ dendritic regions consisted of γ′ precipitates surrounded by the matrix, with a mean size ranging from 0.203 to 0.250 μm, depending on the casting parameters. The amount of the MC carbides in the interdendritic spaces was in the range of 1.87–1.92%. The tensile tests determined that castings produced with preheat temperature of 1566 °C were characterized by higher elongation and slightly lower yield strength in comparison to 1510 °C.

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Effects of Grain Boundary Microconstituents on Heat-Affected Zone Cracks in a Mar-M004 Weldment

Cited by 3 publications

References 36 publications

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

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

The Comparison of Cracking Susceptibility of IN52M and IN52MSS Overlay Welds

Microstructure and selected properties of the solution heat-treated MAR-M247 Ni-based superalloy fabricated via directional solidification

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