Thermal barrier delamination problem

[Hector Monjardin]

Dear experts,

I have a delamination problem in the thermal barrier coating of a plaque who is exposed to 950 C. I used Nicroloy like bond coat (0.004 in) and Ytrria Zirconia (0.012 in) We used the Plasma 7MC equipment with the next parameters:
Hydrogen Pressure/ 70 psi
Hydrogen flow/ 15 SCFH
Argon pressure/ 100 psi
Argon flow/ 100 SCFH
Amp./ 500 Amp.
Vol./ 70 V
Standoff D./ 6 in
Feed rate 30 gr/min
Sustrate/ 310SS

I made some test with mild steel substrate using 1000 C and no delamination occured, so I dont know what happen, Do you have any idea about this problem?? what can be the wrong thing??

Thank you very much

Hector Monjardin

[Vadim Verlotski]

Hi Hector,

There are two important conditions for the functioning of thermal barrier coatings at temperatures above 900°C:

1. Basic material has a nickel-based alloy (Inconel or Nimonic).
2. Bond coat must consist of MCrAlY alloy (better NiCoCrReAlY alloy).

All other base materials and bond coats can not be used at temperatures above 800°C due oxidation of the bond coats and diffusion between the substrate and bond coat. Oxidation and spalling of the bond coat can be clearly seen on the image.

Regards

Vadim

[Joris Kraak]

Hi Hector,

The base material is a 310SS that should not be a problem right, it should suitable for these higher temperatures?

Maybe bondcoating too porous?

regards,
Joris