Investigation of the Effects of Different Types of Investments on the Alpha-Case Layer of Ti6Al7Nb Castings

Authors

  • Mustafa Altindis,

    Corresponding author
    1. Faculty of Engineering and Computer Science, University of Applied Sciences Osnabrück, Albrechtstr. 30, 49076 Osnabrück, (Germany)
    • Faculty of Engineering and Computer Science, University of Applied Sciences Osnabrück, Albrechtstr. 30, 49076 Osnabrück, (Germany).
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  • Katrin Hagemann,

    1. Foundry Institute RWTH Aachen University, Gießerei-Institut RWTH Aachen Intzestraße 5, D-52072 Aachen, (Germany)
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  • Andreas Bührig- Polaczek,

    1. Foundry Institute RWTH Aachen University, Gießerei-Institut RWTH Aachen Intzestraße 5, D-52072 Aachen, (Germany)
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  • Ulrich Krupp

    1. Faculty of Engineering and Computer Science, University of Applied Sciences Osnabrück, Albrechtstr. 30, 49076 Osnabrück, (Germany)
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  • Financial support by the Deutsche Forschungsgemeinschaft (DFG) of an interdisciplinary research group under grants KR1999/11, BU1072/13, BE 1339/32, and SCHN 976/1 is gratefully acknowledged.

Abstract

The effects of four different types of investment on the alpha-case layer of Ti6Al7Nb (Ti67) castings are summarized. The formation mechanism of the alpha-case layer is investigated. Four different investment materials are compared. The alpha-case layers on castings produced with Invest-Ti[BOND]T[BOND], Al2O3[BOND], and ZrSiO4-based investments comprise an oxide layer, an alloy layer, and a hardening layer, and are not only formed by interstitial oxygen but also by substitutional elements dissolved from mould materials. The Y2O3-based investment material provides the most-reliable choice for the production of titanium castings and is beneficial for the casting of Ti67 because of no alpha-case formation.

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