The application of defect maps in the process modeling of single-crystal investment casting

Tu, John; Foran, R. Kelly

doi:10.1007/bf03222250

Cited by 11 publications

(9 citation statements)

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“…The presence of these undesirable grain defects, which lower the crystal solidification. [8,12,13,18] Preventing the formation of grain defects during solidificreep and fatigue properties, could potentially result in the premature failure of critical components. Early efforts taken cation becomes more complicated when dealing with noncylindrical castings.…”

Section: Introductionmentioning

confidence: 99%

“…[7,15] Making assumptions for the shape profiles can be optimized to a certain degree to prevent the formation of defects due to component geometry. [11][12][13][14]19,20] S. TIN or tungsten in the alloy minimizes the onset of freckling convection. [3,21] Although freckles and misoriented grains SX-6 6.3 5.0 11.5 0.18 6.5 6.0 6.5 0.5 -bal can potentially be reduced by optimizing the levels of tanta- bides.…”

Section: Introductionmentioning

confidence: 99%

“…Although the macroscopic criteria for predicting grain-defect formation assume uniform thermal gradients, gradient (G) and withdrawal rate (R)), the initiation of convective instabilities can be minimized. [1,3,[11][12][13][14][15] Criteria for transitions in geometry may result in localized changes of the solidification parameters, which can potentially initiate the development of convective instabilities have often been expressed in terms of dimensionless thermal and solutal convective fluid flow and lead to freckle formation. [14] Currently, through solidification modeling, mold-withdrawal Rayleigh numbers.…”

Section: Introductionmentioning

confidence: 99%

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Stabilization of thermosolutal convective instabilities in Ni-based single-crystal superalloys: Carbon additions and freckle formation

Tin

Pollock

Murphy

2001

Metall Mater Trans A

108

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The effect of carbon additions on the solidification characteristics of single-crystal Ni-based superalloys has been studied over a range of composition with large variations in Re, W, and Ta. Under constant processing conditions, nominally similar experimental alloys containing additions of 0.1 wt pct C exhibited a decreased tendency to develop grain defects, such as freckle chains. The carbon additions resulted in the formation of Ta-rich MC carbides with three distinct morphologies: blocky, nodular, and script. These carbides all precipitate near the liquidus temperature of the alloy. Intentional carbon additions also affected the segregation behavior of the constituent elements. Comparison of experimentally measured distribution coefficients assessed via application of a Scheil-type analysis revealed reduced segregation of Re, W, and Ta in experimental single-crystal alloys containing carbon. The mechanisms by which carbon additions influence freckle formation are considered.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stabilization of thermosolutal convective instabilities in Ni-based single-crystal superalloys: Carbon additions and freckle formation

Tin

Pollock

Murphy

2001

Metall Mater Trans A

108

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“…The present needs of many foundries are being satisfied by relatively simple heat conduction modeling that reedy indicate regions of risk for shrinkage porosity. Coupled with empirical experience, foundry engineers successfi.dly cast parts used in life critical applications (e.g., jet engine turbine components [1]). However, DOE's vision is to move from empiricism to science based design.…”

Section: Mathematical Formulationmentioning

confidence: 99%

Modeling of casting microstructures and defects

Shapiro¹,

Summers²,

Eckels³

et al. 1997

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3. 4. 1.Art Shapiro (MWNTED) -project leader, theoretical developments and experiment design Leonard Summers (C&MS) -Appendix 2 Physical Properties of Solid and Liquid Uranium Del Eckels (MWNTED) -experiment fabrication and execution Vivek Sahai (ME/NTED) -GLO code optimization calculations IntroductionOur interest in casting is linked to DOE efforts to reduce hazardous waste and scrap produced by metal component fabrication processes. Improved processes for manufacturing plutonium and uranium components, for example, can minimim scrap metal, contaminated waste, and possible radiation exposure, and reduce the cost of equipment and facilities.Casting is an ancient art that has been a trial-and-em' process for more than 4000 years. To predict the size, shape, and quality of a cast pmduc~casting manufacturers typically cast fidl-sim prototypes. If one pat of the process is done incorrectly, the entire process is repted until SIIacceptable product is achieved.One way to reduce the time, COSL and waste associated with casting is to use computer modeling to predict not only the quality of a product on the macro-scale, such as distortion and part shape, but also on the micro-scale such as grain defects. Modeling of solidification is becoming increasingly feasible with the advent of parallel computers. Them am essentially two approaches to solidification modeling. The first is that of macro-modeling where heat transfer codes model latent heat release during solidification as a constant and based solely on the local temperature. This approach is useftd in pdicting large scale distortion and final part shape. The second approach, micro-modeling, is more fimdamental. The micro-models estimate the latent heat release during solidification using nucleation and grain growth kinetics. Micro-models give insight into cast grain morphology and show promise in the future to pndict engineering properties such as tensile strength.The micro-model solidification kinetics can be evaluated using first principles or they can be evaluated using experiments. This work describes an implementation of a micro-model for uranium which uses experimental results to estimate nucleation and growth kinetics. Mathematical FormulationThe primary and most obvious phenomenon controlling casting is the transfer of heat fmm the cooling metal to the mold and surroundings. The present needs of many foundries are being satisfied by relatively simple heat conduction modeling that reedy indicate regions of risk for shrinkage porosity. Coupled with empirical experience, foundry engineers 1 successfi.dly cast parts used in life critical applications (e.g., jet engine turbine components[1]). However, DOE's vision is to move from empiricism to science based design. V @ groti law constant 3.Oe-06 m /s C* Heat conduction analvsis codes model latent heat release during solidification as a constant and based solely on&e local temperature. The next step in soli-tication modeling is to make the latent heat a function of the solidification fraction which depends on the n...

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“…[36][37][38][39] Increases in computational speed have allowed these stimulations to be efficiently extended to three dimensions for simplified geometries in axisymmetric configurations. [14,[40][41][42][43][44][45][46][47][48] Unfortunately, the models are not yet able to rigorously simulate the conditions of a directional solidification casting with intricate three-dimensional geometry in a reasonable time period, due to the complexity of the thermal and fluid processes. More accurate and fully three-dimensional analyses will be very important in accounting for casting geometry and nonaxial heat extraction, which have been shown experimentally to have a significant impact on dendrite arm spacing and crystallographic growth orientation.…”

Section: Introductionmentioning

confidence: 99%

Thermal Analysis of the Bridgman and Liquid-Metal-Cooled Directional Solidification Investment Casting Processes

Elliott¹,

Pollock

2007

Metall Mater Trans A

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Thermal profiles obtained during directional solidification of Ni-base superalloy castings by the Bridgman and liquid-metal-cooled (LMC) techniques have been used to develop and validate the finite-element models of these processes. Models of the directional solidification processes for the columnar-grain alloy GTD-444 are used to evaluate the various heat-transfer steps and heat extraction modes within each process. This analysis highlights the similarities and the fundamental differences in heat-transfer modes between the two solidification approaches. Ultimately, the unique limiting heat-transfer step of each process is identified. For the stepped plate configuration investigated, heat extraction is limited by radiation from the exterior mold surface in the Bridgman process. Heat transfer between the casting and the interior mold surface is the primary resistance in the LMC process, and heat extraction is enhanced by the lowering coolant temperatures in this process.

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The application of defect maps in the process modeling of single-crystal investment casting

Cited by 11 publications

References 0 publications

Stabilization of thermosolutal convective instabilities in Ni-based single-crystal superalloys: Carbon additions and freckle formation

Stabilization of thermosolutal convective instabilities in Ni-based single-crystal superalloys: Carbon additions and freckle formation

Modeling of casting microstructures and defects

Thermal Analysis of the Bridgman and Liquid-Metal-Cooled Directional Solidification Investment Casting Processes

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