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On the Formation of White‐Spot Defects in a Superalloy VAR Ingot
Author(s) -
Grignard Jean François,
Soller Aude,
Jourdan Julien,
Bellot JeanPierre,
Jardy Alain
Publication year - 2011
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201000366
Subject(s) - superalloy , ingot , materials science , niobium , liquid metal , alloy , metallurgy , vacuum induction melting
For the production of nickel‐based superalloys for the aerospace industry, strict control of the macrostructure of the product is necessary to avoid the appearance of potentially fatal defects. Our study focuses on the prevention of “white spots” in the alloy IN 718. These defects, which are small volumes of a few millimeters of characteristic length, are depleted in niobium. They are known to result from the fall of metal fragments in the liquid pool during VAR processing. According to their history in the liquid metal, these fragments could not being remelted before being trapped in the mushy zone and then give rise to defects. A model calculates the heat transfer in such a precursor to simulate its melting during his stay in the bath. The validation of the predicted melting kinetics requires a series of immersive experiences of synthetic defects in a metal bath. The model and experiments have demonstrated the initial solidification of a layer of metal around the precursor.