Characterisation of anode plasma deposited IN718 TBC system after thermal cycle shocking test

2

ABSTRACT

The coating that creates a barrier for high temperatures is called as thermal barrier coating (TBC). Yttria-stabilised Zirconia (7–8YSZ (7–8 wt% Y2O3ZrO2)) is characterised after taking a thermal cycling test in a muffle furnace. The specimen is obtained from IN718, which is a nickel-based super alloy and coated by using anode plasma coating technique. Then, the specimen is allowed to heat in muffle furnace for fatigue testing at 1100°C. The holding time for the specimen is 45 minutes and then it is allowed for air cooling. The testing is done to analyse the microstructure of coating before and after thermal fatigue using various microscopy. The delamination of the TBC from the specimen surface is the outcome of the Thermal Fatigue Testing (TFT). Then, the failed specimen is characterised by various techniques like Scanning Electron Microscopy and Transmission Electron Microscopy for microstructure characterisation and material identification. Mismatching of the thermal expansion coefficients of the substrate and coating material is the reason for the more thermal gradients in between the bond coat and top coat. The spallation originated from the corners of the specimen due to the microvoids after TFT and frequent cooling.

KEYWORDS:

• Air plasma spray (APS) coating
• delamination
• electron microscopy
• thermal barrier coating
• thermal fatigue

Disclosure statement

No potential conflict of interest was reported by the author(s).