Analysis of brazing effects on hot corrosion behavior of an aerospace superalloy
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Date
2017
Authors
Esmaeili, Niyousha
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Abstract
Hot corrosion is a predominant type of degradation that takes place in gas turbine engine
components. Wide-gap brazing is a commonly used method for joining extremely difficult-to-weld aerospace materials such as the superalloys used in gas turbine engines. Therefore, effects of brazing and use of different interlayer materials on hot corrosion resistance of brazed IN738 superalloy were studied. Brazing was observed to result in significant reduction in the hot corrosion resistance of the superalloy. However, application of composite powder mixture, which consists of additive superalloy powder, enhanced the hot corrosion resistance of brazed samples. It is also found that although the use of composite powder mixture increased hot corrosion resistance of brazed alloy, if the additive powder completely melts, which is possible during brazing, it can significantly reduce the hot corrosion resistance of the brazed joint. Elemental micro-segregation during solidification of the joint with completely melted powder mixture produces chromium depleted zones and consequently reduces hot corrosion resistance, since a
uniform distribution and adequate chromium concentration is necessary to combat hot corrosion. This has not been previously reported in the literature and it is crucial to the use of composite powder mixture for enhancing the properties of brazed superalloys.
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Keywords
Brazing, Hot corrosion, Superalloy