03-01-2013, 04:47 PM
Uncertainties in Thermal Barrier Coating Life Prediction
1Uncertainties in Thermal.ppt (Size: 691 KB / Downloads: 83)
Thermal Barrier Coating (TBC) Life
Overview:
Thermal barrier coating life is usually predicted based on oxidation life of the bond coating. The effect of thermal fatigue on coating life has been studied but is generally not included in life predictions due to the complex crack dynamics and interactions with the coating and substrate. An attempt to quantify the effect of different thermal cycling on coating life is made using test data.
Method:
Coating life data was obtained from multiple sources and tested in multiple test cells.
Data analysis is first done to determine a coating life for the base test cycle (short cycle). This is to quantify the manufacturing and test variation and give an accurate life number for comparison.
The data for the long cycle will then be compared to the base short cycle coating life to determine if a difference in coating life can be detected.
Failure data fitted using Weibull distribution.
Can mimic behavior of normal, exponential, and other distributions
Will not predict negative lives
Functions from multiple sample sets can be combined to predict an overall population life.
Can be used to fit small data samples.
Conclusions
Coating life is extremely variable.
Coating life may vary by a factor of 3x or more within coatings produced by the same source.
Test conditions can introduce significant variation in addition to the actual coating life variation by source.
Differences in coating life due to thermal cycle damage is small compared to production and testing differences.
Life predictions for thermal barrier coatings are limited by the consistency of production and testing.