Control of Solidification Structure in VAR and ESR Processed Alloy 718 Ingots

Yu, Kai; Domingue, J. A.

doi:10.7449/1989/superalloys_1989_33_48

Cited by 12 publications

(6 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As shown in Figure 11 , freckle defects occurred near both the internal and external interfaces if the height and specimen section size were in the range of freckle tendency. In the previous work [ 20 , 21 , 22 , 23 , 24 , 25 , 26 ], freckle chains were observed inside superalloy parts, especially in the center to mid-radius of VAR/ESR ingots and superalloy billets. A model sketch of freckle formation and the associated fluid flow pattern for internal freckles was applied in Figure 20 a. Freckle defects were caused by fluid flow named thermosolutal convection, originating in the interdendritic region of the mushy zone during solidification.…”

Section: Discussionmentioning

confidence: 91%

Freckle Defect Formation near the Casting Interfaces of Directionally Solidified Superalloys

Hong

Wang

et al. 2016

Materials

View full text Add to dashboard Cite

Freckle defects usually appear on the surface of castings and industrial ingots during the directional solidification process and most of them are located near the interface between the shell mold and superalloys. Ceramic cores create more interfaces in the directionally solidified (DS) and single crystal (SX) hollow turbine blades. In order to investigate the location of freckle occurrence in superalloys, superalloy CM247 LC was directionally solidified in an industrial-sized Bridgman furnace. Instead of ceramic cores, Alumina tubes were used inside of the casting specimens. It was found that freckles occur not only on the casting external surfaces, but also appear near the internal interfaces between the ceramic core and superalloys. Meanwhile, the size, initial position, and area of freckle were investigated in various diameters of the specimens. The initial position of the freckle chain reduces when the diameter of the rods increase. Freckle area follows a linear relationship in various diameters and the average freckle fraction is 1.1% of cross sectional area of casting specimens. The flow of liquid metal near the interfaces was stronger than that in the interdendritic region in the mushy zone, and explained why freckle tends to occur on the outer or inner surfaces of castings. This new phenomenon suggests that freckles are more likely to occur on the outer or inner surfaces of the hollow turbine blades.

show abstract

Section: Discussionmentioning

confidence: 91%

Freckle Defect Formation near the Casting Interfaces of Directionally Solidified Superalloys

Hong

Wang

et al. 2016

Materials

View full text Add to dashboard Cite

show abstract

“…An advantage of ESR is that the molten slag acts as a refining agent to remove oxide clusters. [3][4][5][6][7] VAR is less prone to positive segregation than ESR and is, therefore, capable of melting larger ingots. However, ESR is more resistant to the formation of "white spots" or negative segregation.…”

Section: Ingot Productionmentioning

confidence: 99%

The structural evolution of superalloy ingots during hot working

Jones¹,

Jackman²

1999

JOM

View full text Add to dashboard Cite

Editor's Note: A hypertext-enhanced version of this paper can be found on JOM's web site at www.tms.org/pubs/ journals/JOM/9901/ForbesJones-9901.html.This article provides an overview of structural changes that occur during the hot working of superalloys and provides insight into the use of precipitated particles and other thermomechanical factors to achieve desired structures. Examples will focus primarily on alloys 718 and 720, which are iron-nickel and nickel-based alloys, respectively. The availability of a second phase to control grain size is a characteristic of some iron-nickeland nickel-based superalloys that is not usually available to cobalt-based superalloys; processing with and without the use of a precipitated phase that influences microstructures will be illustrated by the use of these examples. ABOUT THE AUTHORSRobin M. Forbes Jones earned his Ph.D. in metallurgy at Imperial College of Science and Technology, London University, in 1967. He is currently manager of long-range product/ process R&D for Allvac.Laurence A. Jackman earned his Ph.D. in metallurgy at Rensselaer Polytechnic Institute in 1967. He is currently chief materials scientist at Allvac. Dr. Jackman is also a member of TMS.For more information, contact R.M. Forbes Jones,

show abstract

“…"Dendritic pattern", or "residual dendritism" has been defined in terms of micro segregation that may be observable macroscopically (3). If severe enough, either condition may be cause for rejection.…”

Section: Macrostructurementioning

confidence: 99%

“…The resultant improvement in oxide cleanliness is a major benefit associated with the VIM+ESR route (3,4,5). A drawback of VIM+ESR material is its greater tendency, relative to VIM+VAR material, to contain regions of chemical segregation, especially along the center of large diameter ingots.…”

Section: Introductionmentioning

confidence: 99%

Advances in Triple Melting Superalloys 718, 706, and 720

Moyer¹,

Jackman²,

Adasczik³

et al. 1994

Superalloys 718, 625, 706 and Various Derivatives (1994)

View full text Add to dashboard Cite

Triple melting (TM) by VIM+ESR+VAR has been highly successful for Alloy 718, large diameter ingots of Alloy 706, and high hardener alloys such as Alloy 720. Frequencies of ultrasonic indications for TM 718 are significantly lower than for VIM+VAR melt 718 because fewer clusters of inclusions are present, The cleanliness associated with TM 718 was verified by microscopy and by electron beam melting of buttons after VIM, VIM+ESR, and TM. Furthermore, white spot frequencies were found to be reduced for TM 718. Ultrasonic defect frequencies of Alloy 706 and Alloy 720 are also low. A major advantage of triple melting Alloy 706 is that ingots up to 36 inches (914mm) in diameter can be melted without freckles or positive segregation problems.

show abstract

Control of Solidification Structure in VAR and ESR Processed Alloy 718 Ingots

Cited by 12 publications

References 0 publications

Freckle Defect Formation near the Casting Interfaces of Directionally Solidified Superalloys

Freckle Defect Formation near the Casting Interfaces of Directionally Solidified Superalloys

The structural evolution of superalloy ingots during hot working

Advances in Triple Melting Superalloys 718, 706, and 720

Contact Info

Product

Resources

About