Hi Powerman
Approximate coefficient of expansion (in/in degree C x 10^6)
Metco 204 10 (source Metco )
Alumina ~8
Which is generally a little less, but similar to your typical steels and nickel chromium alloys, but very different (1/2 to 1/3 less) to austenitic stainless steels and aluminium.
The stress build-up in the coating due to particle solidification is probably a much larger consideration. Knowing the coatings thickness limitation is a very useful guide. Coefficient of expansion differences between coating and substrate will probably be more important with regard to high temperature changes during service than the relatively small temperature changes seen during spraying (100 C or so), but it can have an accumulative positive or negative effect on stress levels.
Quote:For TBC coating, normally bond coat I spray 0.15mm thinkness, top coat 0.30mm thickness.
I don't think you should really have any problems at these thickness's.