Thermal Fatigue Behavior of Thick and Porous Thermal Barrier Coatings Systems

Abstract

High-temperature thermal fatigue causes the failure of thermal barrier coating (TBC) systems. This paper addresses the development of thick TBCs, focusing on the microstructure and the porosity of the yttria partially stabilized zirconia (YPSZ) coating, regarding its resistance to thermal fatigue. Thick TBCs, with different porosity levels, were produced by means of a CoNiCrAlY bond coat and YPSZ top coat, both had been sprayed by air plasma spray. The thermal fatigue resistance of new TBC systems and the evolution of the coatings before and after thermal cycling was then evaluated. The limit of thermal fatigue resistance increases depending on the amount of porosity in the top coat. Raman analysis shows that the compressive in-plane stress increases in the TBC systems after thermal cycling, nevertheless the increasing rate has a trend which is contrary to the porosity level of top coat.

Failure Mechanism for Thermal Fatigue of Thermal Barrier Coating Systems

“…After the thermal cycling test, no detectable change of the phase composition of the top coat was observed, according to x-ray diffraction analysis and Raman spectroscopy as shown in a previous paper (Ref 31).…”

Recent Activities in the Field of Thermal Barrier Coatings Including Burner Rig Testing in the European Union

“…The last technology is established at the University of Firenze [56] allowing structural characterization of ceramic materials, evaluation of strain and stress, structural and spot analysis (Raman spot ≈ 100 lm, MicroRaman spot ≈ 1 lm), and phase modification.…”

Development and Investigation on New Composite and Ceramic Coatings as Possible Abradable Seals

“…Three different kinds of TBC systems were coated by APS on circular substrates (diameter: 25 mm; thickness: 3 mm) of HX with the same bond coat of AMDRY 995 (average thickness of 250 lm) and with a top coat of yttria partially stabilized zirconia powder (Amperit 827.7 produced by H.C. Starck) (average thickness of about 1.8 mm) and low (17 ± 1%) (Sample 5), medium (21 ± 1%) (Sample 6), and high (29 ± 1%) (Sample 7) porosity levels of the top coat as described in previous papers [6,7].…”

“…The ceramic filler particles embedded in the metal matrix should improve the abradability due to their brittleness as it occurs for metal matrix with solid lubricant (Ref 4). Thick and porous thermal barrier coating (TBC) systems were also produced by APS without using plastic filler ( Ref 6,7) in the sprayed powder. The oxidation resistance of composite coatings and thermal fatigue resistance of thick and porous TBC systems were assessed according to original engine manufacturer (OEM) specifications by means of isothermal and cyclic oxidation tests, and their abradability was evaluated.…”