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

Wide Gap Braze Repair Using Vertically Laminated Repair Scheme

[+] Author and Article Information
Doug Nagy

 Liburdi Turbine Services, Dundas, ON, L9H 7K4, Canada

Xiao Huang1

 Liburdi Turbine Services, Dundas, ON, L9H 7K4, Canada

1

Also at Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, ON, K1S 5B6, Canada.

J. Eng. Gas Turbines Power 131(1), 012101 (Oct 13, 2008) (7 pages) doi:10.1115/1.2967496 History: Received April 01, 2008; Revised April 02, 2008; Published October 13, 2008

Repair of after-service gas turbine hot section superalloy components provides considerable saving in life-cycle cost of engines. Whereas a number of methods have been used in the past to repair these superalloy components, wide gap brazing technology has provided a practical alternative to repair difficult-to-weld alloys with substantial damages. In this paper, the historical development of wide gap repair technologies is reviewed first. Subsequently, the recent development in utilizing a vertically laminated structure to repair a large and deep gap (up to 16 mm) in one brazing cycle will be discussed. The microstructure resulted from this repair scheme will be evaluated and compared with conventional wide gap braze with slurry and that of the Liburdi powder metallurgy (LPM™) process. It is observed that in conventional wide gap brazing with premixed slurry, the presence of intermetallic compounds can be effectively reduced by reducing the ratio of braze alloy to gap filler, which, however, also contributes to the increased occurrence of macroscopic voids in the wide gap joint. The LPM™ method, on the other hand, can achieve a macroscopically void-free repair of gap (up to 6 mm) and minimize the formation of intermetallics. By using a vertically laminated repair scheme it is shown that the process is able to repair a deeper gap (up to 16 mm) with no macroscopic defects and reduced intermetallic compounds.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Conventional wide gap brazing with slurry

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Figure 2

LPM™ wide gap joint (a) and a vertically laminated structure (VLS) (b) (the width at the top of the cavity is about 1 mm in this configuration)

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Figure 3

IN738 (a) BNi-9 powder (b) in the as-received condition

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Figure 4

40% BNi-9 WGB joint by slurring method showing a 2 mm interstitial void

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Figure 5

Microstructure (BSE) and EDS maps of the WGB joint with 40% BNi-9; large Cr boride phases are observed to co-exist with a finer Ti boride phase (14)

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Figure 6

WGB joint with 30% BNi-9 and 70% IN738 (14)

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Figure 7

WGB joint with 20% BNi-9; the size of Cr-rich boride has been reduced in comparison to Figs.  56(14)

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Figure 8

WGB repaired joints using LPM™ (a) and vertically laminated configuration (b)

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Figure 9

Microstructure of WGB repaired joints using LPM (a) and a vertically laminated structure (b)

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