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Journal of Materials Science

, Volume 30, Issue 20, pp 5151–5160 | Cite as

Transient liquid-phase bonding of ferritic oxide dispersion strengthened superalloy MA957 using a conventional nickel braze and a novel iron-base foil

  • T. I. Khan
  • E. R. Wallach
Article

Abstract

It has been shown that an iron foil based on the Fe-B-Si system is a suitable material for use as a high-temperature interlayer for transient liquid-phase (TLP) bonding of ferritic oxide dispersion strengthened alloys. TLP bonding produced ferritic joints, free from intermetallic precipitates and identical in composition to that of the parent metal. In contrast, however, TLP bonding using the nickel-base foil, Bni1a, resulted in an austenitic bond region stabilized by the high nickel concentration. Furthermore, the retention of the melting point depressants, particularly silicon, at the centre of the joints resulted in the bond solidifying with the formation of silicide-boride precipitates both at the bond centre and at the braze/parent metal interface. High-temperature heat treatments failed to remove the γ-Fe phase and the precipitates, and their presence detrimentally affected the mechanical properties of the joint. The formation of intermetallic precipitates at the braze centre has been attributed to the initial high concentration of chromium present in the Bni1a brazing foil. Preliminary mechanical tests showed that bond strengths of joints made using the iron-base foil were superior to those obtained using the commercial nickel braze. When the iron-base foil was used, bond strengths both at room temperature and at the service temperature (700 °C) were near parent metal strengths. However, at room temperature, failure was observed to occur away from the bond interface, whilst at elevated temperatures, joints failed along the bond interface; this was attributed to the effects of melt-back phenomenon characteristic in TLP bonding.

Keywords

Parent Metal Iron Foil Oxide Dispersion Strengthened Alloy Intermetallic Precipitate Point Depressant 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Chapman & Hall 1995

Authors and Affiliations

  • T. I. Khan
    • 1
  • E. R. Wallach
    • 1
  1. 1.Department of Material Science and MetallurgyUniversity of CambridgeCambridgeUK

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