Alloys or metallic compositions – Cobalt base – Chromium containing
Patent
1997-04-08
1999-06-29
Yee, Deborah
Alloys or metallic compositions
Cobalt base
Chromium containing
420437, 420436, 420439, 420435, 148425, 148408, 22826231, C22C 1907
Patent
active
059165189
ABSTRACT:
An improved cobalt-base braze alloy composition and method for diffusion brazing are provided for use in repairing superalloy articles, such as gas turbine engines, power generation turbines, refinery equipment, and heat exchangers. The improved cobalt-base braze alloy composition includes nickel; at least one element selected from the group of rhenium, palladium, and platinum; at least one element selected from the group of boron and silicon; and the remaining balance consists of cobalt. This composition may also include aluminum, and the composition may be combined with one or more powdered base metal superalloy compositions to form an improved diffusion braze alloy mixture. In the improved method for repairing superalloy articles, the foregoing mixture is applied to a region of the superalloy article to be repaired. The mixture is then heated to melt the cobalt-base braze alloy, thereby joining the base metal superalloy powder particles together, and joining the entire mixture to the region being repaired. The molten mixture is next subjected to a diffusion braze heat treatment cycle in order to break down undesirable boride and silicide phases and to diffuse the melting point depressants into the mixture. In a preferred embodiment, the long term diffusion heat treatment cycle consists of heating the repaired article to 2000.degree. F., holding that temperature for 2 hours, heating the repaired article to 2100.degree. F., holding that temperature for 22 hours, and cooling the article to 250.degree. F. After cooling, an environmental coating is applied to the final repair composite, and this composite significantly improves the cyclic oxidation resistance of the coating compared to the properties of the superalloy base metal.
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Allison Engine Company
Yee Deborah
LandOfFree
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