Abstract:AD730 TM Ni-based superalloy specimens in solution-treated conditions were linear friction welded. Then, post-weld heat treatment (PWHT), consisting of γ´ sub-solvus solution treatments followed by aging, was conducted on the linear friction welded samples. High temperature creep tests were performed on the as-welded and PWHTed joints at two different temperatures: 700°C under 600 and 750 MPa stress levels, and 850°C under 100 and 200 MPa stresses. The creep resistance of the PWHTed joints was higher than that… Show more
“…7(a-d), a large number of dimple like features that are visible at the fracture surface. Such surface characteristics have already been also reported in other superalloys [35,40,41]. They have been related to the growth (Fig 7 a and b) and coalescence of voids (Fig.…”
Section: Fracture Surface Analysissupporting
confidence: 81%
“…Specifically, the authors reported that the occurrence of liquation in the vicinity and within grain boundaries degraded the ductility of the alloy under tension and, as such, the alloy failed without plastic deformation [50]. Furthermore, as reported by other investigators [34,37,40], complete dissolution of γ' particles in the matrix of AD730 TM occurred at 1200ºC which resulted in significant weakening of the grain boundaries in which liquation could occur. In general, intergranular cracking at high temperatures takes place at locations with localized stress or structural imperfections such as the grain boundary edges, triple points, and interface of brittle particles and are accompanied with grain boundary slipping and the formation voids [36,51,52].…”
Section: Analysis Of the Flow Curvesmentioning
confidence: 75%
“…They have been related to the growth (Fig 7 a and b) and coalescence of voids (Fig. 7 c and d), and cavities nucleated at grain boundaries which have been connected to the surface and assisted surface crack growth due to the reduction of the surface area resulting in the formation of a large number of microvoids that produce a dimpled crack surface [35,[40][41][42]. For the low heating rate, void coalescence could take place and the dimples appear larger, while for the fast heating rate very small dimples are observed at the fracture surface.…”
Hot ductility of the newly developed AD730 TM nickel-base superalloy was investigated in the temperature interval 1050-1240°C. The nil strength and nil ductility temperatures were determined by hot tensile testing using the Gleeble TM 3800 weld thermal simulation method. The influence of heating rate, representing the weld thermal cycle, on hot ductility behavior of the alloy was also investigated. The microstructure and the fracture mode of samples were examined by optical and scanning electron microscopy. The influence of heating rate on the extent of grain boundary liquation and void formation was determined and it is shown that the significant ductility loss near the NDT point could be related to the reduction of surface tension at the grain boundary-matrix interface. In addition, the contribution of hard precipitates, such as grain boundary MC carbides, voids, and cavities as other damage mechanisms responsible for ductility loss at high temperature, are discussed.
“…7(a-d), a large number of dimple like features that are visible at the fracture surface. Such surface characteristics have already been also reported in other superalloys [35,40,41]. They have been related to the growth (Fig 7 a and b) and coalescence of voids (Fig.…”
Section: Fracture Surface Analysissupporting
confidence: 81%
“…Specifically, the authors reported that the occurrence of liquation in the vicinity and within grain boundaries degraded the ductility of the alloy under tension and, as such, the alloy failed without plastic deformation [50]. Furthermore, as reported by other investigators [34,37,40], complete dissolution of γ' particles in the matrix of AD730 TM occurred at 1200ºC which resulted in significant weakening of the grain boundaries in which liquation could occur. In general, intergranular cracking at high temperatures takes place at locations with localized stress or structural imperfections such as the grain boundary edges, triple points, and interface of brittle particles and are accompanied with grain boundary slipping and the formation voids [36,51,52].…”
Section: Analysis Of the Flow Curvesmentioning
confidence: 75%
“…They have been related to the growth (Fig 7 a and b) and coalescence of voids (Fig. 7 c and d), and cavities nucleated at grain boundaries which have been connected to the surface and assisted surface crack growth due to the reduction of the surface area resulting in the formation of a large number of microvoids that produce a dimpled crack surface [35,[40][41][42]. For the low heating rate, void coalescence could take place and the dimples appear larger, while for the fast heating rate very small dimples are observed at the fracture surface.…”
Hot ductility of the newly developed AD730 TM nickel-base superalloy was investigated in the temperature interval 1050-1240°C. The nil strength and nil ductility temperatures were determined by hot tensile testing using the Gleeble TM 3800 weld thermal simulation method. The influence of heating rate, representing the weld thermal cycle, on hot ductility behavior of the alloy was also investigated. The microstructure and the fracture mode of samples were examined by optical and scanning electron microscopy. The influence of heating rate on the extent of grain boundary liquation and void formation was determined and it is shown that the significant ductility loss near the NDT point could be related to the reduction of surface tension at the grain boundary-matrix interface. In addition, the contribution of hard precipitates, such as grain boundary MC carbides, voids, and cavities as other damage mechanisms responsible for ductility loss at high temperature, are discussed.
“…IN718 is a high strength superalloy extensively used for blade applications in gas turbines due to its good weldability and excellent resistance to cracking [20][21][22]. AD730 TM is a Ni-based alloy recently developed by Auber & Duval Company as a new forged Ni-based superalloy for turbine disk applications, and its mechanical properties are comparable to those of other Ni-based superalloys such as Waspaloy, Udimet720 and IN718Plus [13,14,[23][24][25].…”
Selective Laser Melted (SLM) Inconel718 (IN718) superalloy was linear friction welded (LFWed) to forged AD730 TM Nickel-based superalloy. Successful joints free of micro-porosity, micro-cracking, and oxides were obtained. Microstructure variations across the weld line developed during LFW were examined using different techniques, including laser confocal microscopy, scanning electron microscopy, energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD). The microstructure was also evaluated, particularly in terms of Grain size and misorientation changes were determined and correlated with microhardness evolution in different regions of the weld joint. The characteristics of the microstructure on both sides of the weld joint was analyzed and related to the deformation and temperature paths imposed during the LFW process. Dynamic recrystallization (DRX) occurred on both sides of the dissimilar weld line and it was found that Discontinuous DRX (DDRX) and Continuous DRX (CDRX) took place in the WZ and in the TMAZ, respectively. In order to study the influence of the starting microstructure in the LFW experiments, LFW of a homogenized SLM IN718 sample was analyzed and compared with the non-homogenized sample. A clear change in the size and grain misorientation levels of the heat and thermomechanical affected zones were observed between the two conditions. The differences were related to a greater degree of strain induced in homogenized sample and the increasing effect of the solid solution strengthening mechanism caused by a partial dissolution of the second-phase strengthening particles in the matrix.
“…19–21 There is a high demand in using computational methods to predict the material thermal processes and material deformation. 22–24 So far, there has been extensive research on LFW, in relation to studies on the welding processes, 25–29 microstructural characterization, 30–33 numerical simulation, 11,34–39 and analytical computation. 35,40–43 Figure 1.Linear friction welded integrally bladed-disk (blisk) manufactured at TWI.…”
This paper presents a fully coupled thermomechanical model for the linear friction welding process of Inconel-718 nickel-based superalloy by using the finite element method. Friction heat, plastic work, and contact formulation were taken into account for two deformable plastic bodies oscillating relative to each other under large compressive force. The modelling results of the thermal history at the weldline interface and thermal field at a distance away from the rubbing surfaces were compared to instrumented data sourced from related publications for model verification. Optimal linear friction welding process parameters were identified via comparison of weld temperature to the liquidus temperature of Inconel-718 alloy. Comparison of interface temperature showed a consistent range of values above the solidus melting temperature (1250 ℃) and below the liquidus melting temperature (1360 ℃) of Inconel-718 alloy. For the first time, a visible linear friction welding process window is identified using a thermomechanical computational modelling method. Through computational modelling, the influence of welding process parameters on the heat transfer and deformation of weld was systematically investigated.
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