White Spots in Superalloys

Jackman, L.A.; Maurer, G. E.; Widge, S.

doi:10.7449/1994/superalloys_1994_153_166

Cited by 28 publications

(16 citation statements)

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“…The melting rate of particles in molten metal has been extensively studied in the context of dissolving alloying elements in steel making [20,21]. The same basic formulation is used here.…”

Section: Melting Of a Particle Within The Melt Poolmentioning

confidence: 99%

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Modeling of Vacuum Arc Remelting of Alloy 718 Ingots

Patel¹,

Minisandram²,

Evans³

2004

Superalloys 2004 (Tenth International Symposium)

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Vacuum Arc Remelting (VAR) is typically the final melting process in the production of a wide range of alloys including superalloys, titanium, zirconium and specialty steels. During this process, a DC arc is struck under vacuum between a consumable electrode and a water-cooled copper crucible. The heat from the arc melts the electrode and molten metal droplets from the electrode solidify in the crucible to form an ingot. The purpose of VAR is to cast a sound, segregation free ingot. The soundness of the final structure and tendency for defect formation are determined by the pool profile and ingot solidification patterns during the process. These, in turn, depend on the melting parameters, which change as the ingot freezes. A carefully developed physics-based numerical model is useful in analyzing a priori the effect of melt parameters on the molten metal pool in the ingot. The purpose of this paper is to discuss the key features of such a model, and examine the effect of melting parameters on the pool profile. In addition, the effect of a molten metal pool perturbation during a power interruption and a melt rate cycle is examined for a 0.5m (20-inch) diameter ingot. Finally, the computed temperature distribution and flow field is used to predict the melting time for particles that fall into the molten pool and the likelihood of freckle formation in an alloy 718 VAR ingot.

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“…The melting rate of particles in molten metal has been extensively studied in the context of dissolving alloying elements in steel making [20,21]. The same basic formulation is used here.…”

Section: Melting Of a Particle Within The Melt Poolmentioning

confidence: 99%

“…These could either melt completely or partially depending on their size and the melting conditions. The un-melted particles, usually a few millimeters in size, end up as discrete white spots and are usually seen at the center to mid-radius location in the billet [20].…”

Section: Melting Of a Particle Within The Melt Poolmentioning

confidence: 99%

Modeling of Vacuum Arc Remelting of Alloy 718 Ingots

Patel¹,

Minisandram²,

Evans³

2004

Superalloys 2004 (Tenth International Symposium)

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“…White spots are discrete features in the superalloy billet that are observed after chemical etching. 50 Although compositionally similar, these features are typically less heavily alloyed than the superalloy matrix. Compositions of white spots and freckles in IN718 are listed in Table 6.…”

Section: Vacuum Arc Remeltingmentioning

confidence: 99%

Nickel-Based Superalloys for Advanced Turbine Engines: Chemistry, Microstructure and Properties

Pollock

Tin

2006

Journal of Propulsion and Power

2,058

699

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The chemical, physical, and mechanical characteristics of nickel-based superalloys are reviewed with emphasis on the use of this class of materials within turbine engines. The role of major and minor alloying additions in multicomponent commercial cast and wrought superalloys is discussed. Microstructural stability and phases observed during processing and in subsequent elevated-temperature service are summarized. Processing paths and recent advances in processing are addressed. Mechanical properties and deformation mechanisms are reviewed, including tensile properties, creep, fatigue, and cyclic crack growth.

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“…However, there is a possibility for extrinsic particles or fragments from the VIM electrode to fall into the VAR melt pool, become entrapped within the mushy zone, and survive in the fi nal ingot as white spots. [11][12][13] Knowledge of the distribution in the VIM electrode of such particles and heterogeneous regions (e.g., coarse dendrites in the shrinkage pipe) would be necessary to simulate the formation of such white spots. This phenomenon, which has been addressed by Zhang et al, is the subject of another study.…”

Section: Vacuum Induction Meltingmentioning

confidence: 99%