Discoloration after precipitation heat treatment 1

[ckiyak]

Hi,

I am working as a heat treatment engineer in one of the fastener company. 2 days ago, i saw something interesting. color of the waspaloy parts after heat treatment differed from each other( from purple to black) . Firstly i went to laboratory to check their mechanical and metallurgical properties. I took one part from each color. All values from the experiement showed us all the parts are okay. But i didnt understand how this occured.

My opinion was vacuum level, then i made an experiement. I put some waspaloy part to furnace without vacuum. After 16 hours at 760 C, ,i checked the parts. Results was interesting for me. All of the parts were black. I am really confused right now. Please help. Thanks.

 

[EdStainless]

The colors are most likely due to oxide film on the surface.
When the film is very thin it is clear and you get optical diffraction effects resulting in colors (similar to oil on water). When the film gets thicker it is not transparent and the colors turn dark and dull (gray, brown, black).


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P.E. Metallurgy, Plymouth Tube