Interface Reactions Responsible for Run-Out in Active Brazing: Part 1

Journal Article · 01 February 2018 · Welding Journal

DOI: https://doi.org/10.29391/2018.97.004 · OSTI ID:1429670

Vianco, Paul T. ^[1]; Walker, Charles A. ^[1]; De Smet, Dennis J. ^[1]; Kilgo, Alice C. ^[1]; McKenzie, Bonnie M. ^[1]; Grant, Richard L. ^[1]

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1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

The run-out phenomenon was observed in Ag-Cu-Zr active braze joints made between the alumina ceramic and Kovar™ base material. Run-out introduces a significant yield loss by generating functional and/or cosmetic defects in brazements. A prior study identified a correlation between run-out and the aluminum (Al) released by the reduction/oxidation and the latter’s reaction with the Kovar™ base material. A study was undertaken to understand the fundamental principles of run-out by examining the interface reaction between Ag-xAl filler metals (x=2, 5, and 10 wt.%) and Kovar™ base material. Sessile drop samples were fabricated using brazing temperatures of 965°C or 995°C and times of 5 min or 20 min. The correlation was made between the degree of wetting-and-spreading by the sessile drops and the run-out phenomenon. Wetting-and-spreading increased with Al content (x) of the Ag-xAl filler metal, but was largely insensitive to the brazing process parameters. The increased Al concentration resulted in higher Al contents of the (Fe, Ni, Co)_xAl_y reaction layer. Run-out was predicted when the filler metal has a locally-elevated, Al content exceeding 2 – 5 wt.%. Lastly, several mitigation strategies were proposed, based upon these findings.

• Research Organization: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Security
• Contributing Organization: American Welding Society
• Grant/Contract Number: AC04-94AL85000; NA0003525
• OSTI ID: 1429670
• Report Number(s): SAND-2017-11635J; 658200
• Journal Information: Welding Journal, Vol. 97, Issue 2; ISSN 0043-2296
• Publisher: American Welding SocietyCopyright Statement
• Country of Publication: United States
• Language: English