Research Papers: Gas Turbines: Manufacturing, Materials, and Metallurgy

Effect of Tungsten Addition on the Nucleation of Borides in Wide Gap Brazed Joint

[+] Author and Article Information
Daniel McGuire, Xiao Huang

Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, Ontario K1S 5B6, Canada

Doug Nagy

 Liburdi Engineering, 400 Highway 6 North, Dundas, Ontario L9H 7K4, Canada

Weijie Chen

 NRC Institute for Aerospace Research, 1200 Montreal Road, Building M-17, Room 104, Ottawa, Ontario K1A 0R6, Canada

J. Eng. Gas Turbines Power 132(6), 062101 (Mar 24, 2010) (6 pages) doi:10.1115/1.4000136 History: Received April 16, 2009; Revised April 17, 2009; Published March 24, 2010; Online March 24, 2010

Wide gap brazing (WGB) is a cost effective and reliable means to repair gas turbine hot section components with defect sizes exceeding 0.3 mm. However, it has been shown that WGB joints of nickel-based superalloys suffer from reduced ductility and thermal fatigue life due to the presence of brittle intermetallics and porosities in the brazed joint. In order to disperse the brittle intermetallic compounds, potentially increase the ductility of the repaired region, and reduce the risk of the thermomechanical fatigue failure, elemental tungsten (W) was added to the braze additive filler alloy IN738 by mechanical alloying. The alloyed IN738 was then brazed with the addition of 30 wt %, 50 wt %, and 80 wt % of braze alloy (BNi-9). After brazing at 1200°C for 20 min, microstructural analysis of WGB joints showed a decreasing trend of discrete boride size and the amount of eutectic and script-shaped borides with the increases of W. The increase in the braze alloy to additive filler alloy ratio diminished the effect of W addition due the dissolution of W particulates.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Specimen cutaway showing typical preparation

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Figure 2

Microstructures of samples with varying amount of braze alloy

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Figure 3

EDS spot analysis of various phases in P5G2B30 (a) and P5G2B70 (b)

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Figure 4

Microstructure variation with tungsten addition

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Figure 5

Elemental maps of sample P2G4B50

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Figure 6

Element distribution of P8G4B50

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Figure 7

EDS analysis of sample P8G4B50

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Figure 8

Effect of grinding time on the boride formation and distribution




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