Performance of Vertical Cracked Air Plasma Spray Processed Thermal Barrier Coatings: Thermo-Physical Properties Measurements, and Effects of Thermal Stress on Thermal Cycling Failure

In this study two variations of Air plasma spray (APS) coated Inconel738 (IN738) materials are evaluated for their thermal cycling and spalling behavior as well as thermo-physical properties variations as a function of temperature. The emphasis in this study was to investigate two different processing regimes that yield a standard APS and vertically oriented columnar microstructures in terms of their thermomechanical performance. The thermal cycling studies involved ramping the samples from 25°C to a temperature of about 1125°C in duration of 30 minutes, and followed by maintaining the samples at that temperature for 5 hours, followed by cooling down from 1125°C to 25°C for 30 minutes. The thermal properties measurements involved using Laser Flash method to measure thermal diffusivity and thermal conductivity from 100°C to 900°C. A thermal stress analytical study was also conducted in order to draw inference in the above studies as to the plausible causes of failure in the samples. Preliminary results of this thermal cycling and thermo-physical properties study are presented in this paper. The results are being correlated with the stress analysis results.