TBC Coating change to grey

[mehongbo]

Hi,
Have a question to coating experts. Why the TBC Coating (not sure but think it is 8% YSZ) changes to grey color after part aging, then change back to yellow again after TBC bake-up heat treatment?

Also, the bake-up heat treatment change the TBC more yellowish comapred to as-coated TBC, Is it because the oxidation ? What is the benefit to TBC from backup process? Have anyone seen academic papers talking about this?

Thanks in advance
Hong

[Gordon]

Hi Hong

colour-tbc-t-223.html may be worth reading if you have not already