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Thermal barrier coating; yttria-stabilized zirconia; plasma spraying; thermal conductivity; oxidation resistance.

Thermal barrier coatings (TBCs) of yttria-stabilized zirconia (YSZ) of different thicknesses with an intermediate bond coat were deposited on C-103 Nb alloy using the air plasma spraying technique. The coatings were subjected to rapid infra-red (IR) heating ($\sim$25°C s$^{−1}$) up to $\sim$1250°C and exposed up to 100 s at this temperature with heat flux varying from 55 to 61 Wcm$^{−2}$. The TBCs were found to be stable and intact after the heat treatment. In contrast, at the same conditions, the uncoated C-103 alloy specimen showed extensive oxidation followed by weight loss due to spallation. A maximum temperature drop of $\sim$200°C was observed on the opposite side of the coated alloy with 600 $\mu$m YSZ coat; as against negligible temperature drop in case of bare alloy specimen. The temperature drop was found to increase with the coating thickness of YSZ. The coatings before and after IR heating were investigated by scanning electron microscopy, X-ray diffraction, electron probe microanalysis, microhardness and residual stress measurements in order to understand the effect of thermal shock on the properties of the TBC. On account of these high-temperature properties, YSZ coating along with the bond coat is expected to find potential thermal barrier coating system on niobium alloys for supersonic vehicles.

S S Panwar^{1 2} T Umasankar Patro² K Balasubramanian² B Venkataraman³

1. Defence Research and Development Laboratory, Kanchanbagh, Hyderabad 500 058, Telangana, India
2. Department of Materials Engineering, Defence Institute of Advanced Technology (DU), Girinagar, Pune 411 025, Maharashtra, India
3. Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500 058, Telangana, India

Published

February 2016

Manuscript received

5 September 2015

Accepted

5 October 2015