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

https://www.gordonengland.co.uk/sef/Thread-Colour-TBC may be worth reading if you have not already

[Artyom]

Hi Hong

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

Dear Gordon!

Could you possibly provide another link? This one colour-tbc-t-223.html doesn't work (404 error)

Thanks in advance 

Regards,
Artyom

[Gordon]

Hi Artyom,

https://www.gordonengland.co.uk/sef/Thread-Colour-TBC

[plasmajet1990]

Hi Artyom,

https://www.gordonengland.co.uk/sef/Thread-Colour-TBC

Hello Gordon,


I also encountered this "anomaly", but I did not worry because I had the following explanation in my mind:

The eye perceives the electromagnetic radiation (light) reflected by the analyzed object.
The perceived color is given by the wavelength of the reflected radiation.
The radiation that is not absorbed by the object is reflected and depends on the distance between the atoms (I won't go into details).
In our case, the YSZ layer has a certain crystallization form that determines the distance between atoms.
Very briefly: Depending on the temperature, the YSZ layer changes its crystallization form - changes the distances between atoms - changes the color we perceive.
Between the minutes: 1.57-3.57 and 4.20-5.30 you can see the color change of the samples.


https://www.youtube.com/watch?v=xVVrH89eOug

The parameters used for APS deposition do not influence the color. The temperature of the substrate influences the color.



Ion