Performance of YSZ and Gd2Zr2O7/YSZ double layer thermal barrier coatings in burner rig tests

Unique performance of thermal barrier coatings made of yttria‐stabilized zirconia at extreme temperatures (>1500°C)

“…18 These high energy release rates can explain the earlier failure of TBC systems tested at extremely high surface temperatures of above 1400°C. This reduction was recently observed 19 and a corresponding explanation was given in terms of the energy release maximum during the transient cooling phase of the thermal cycling experiments. It was demonstrated in this investigation that the other degradation mechanisms often assumed to take place at elevated temperatures, namely sintering and monoclinic phase formation, are not of major importance.…”

“…An estimation according to Ref. 19 gives even higher value, in the first 10 ms the cooling rate is about 20 000 K/s.…”

“…The results of the experiments with fast cooling rates are taken from a previous publication. 19 Obviously, the low cooling rate leads to a huge improvement of the lifetime by a factor of more than 2. The lifetimes at a surface temperature of 1550°C with slow cooling seem to be even slightly higher than the one at a surface temperature of 1400°C with fast cooling.…”

“…Lifetime is here defined as the minimal cycle number at which 20% of the TBC coated area spalled‐off. The results of the experiments with fast cooling rates are taken from a previous publication 19 …”

“…An indication of this sintering was found by indentation tests. 19 However the coating is still rather intact showing only some crack formation even after more than 100 hours at 1550°C. Due to the long time at elevated temperature, the TGO also grew much thicker than for the high cooling rate sample, a value of about 6 µm could be determined.…”