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Letter 42087 Discoloration of superalloy part after vacuum heat treatment [Canada]August 30, 2006 We used vacuum furnace to heat treat parts of superalloy (Ni-based materials, such as AMS 5596) at 1600~1800 °F under pretty good vacuum level of 10-4 ~10-5 Torr. Sometimes the parts got discoloration (blue or dark blue). My question: what caused the discoloration and how to prevent it? Max Gui
First of two simultaneous responses -- September 1, 2006 Classic results of oxygen in the system. James Watts
Second of two simultaneous responses -- September 2, 2006 Max, my best guess is that the seal on the door was a bit dirty: we've found that even a hair laid across the door seal is enough to get discoloration. Another source of the contaminant that will cause this kind of problem is if the parts aren't cleaned and dry enough. If you still have a small amount of solvent or soap on them, it'll burn on, or evaporate and discolor, or cause some such thing.
Dear Reader: please choose what you want to do--
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