Synthesis and Application of Nano structured Bi layer YSZ LZ Thermal Barrier Coating
Present work is on synthesis of high purity Nano-structured TBC materials, Lanthanum Zirconate and YSZ. They were prepared via wet chemical routes, starting from the indigenous source minerals such as zircon and monazite available in the beach sand. This is first time that the results of TBC materials synthesis from these base minerals, their purification and a high end application being presented comprehensively. Their characterisation and thermal barrier application on aeroengine components have been presented. The total oxide impurities being critical to the life of the coating, could be controlled within 0.03 per cent by weight. On comparison with other powders it was found that the indigenously synthesised YSZ powder had practically 100 per cent tetragonal prime phase and no monoclinic phase; whereas others had significant amounts of monoclinic phases present in them. Both YSZ and LZ powders were sinter agglomerated at 850 °C to preclude the possibility of any contamination and sieved. APS process was used to realise nano-structured bi-layer coating on the exhaust nozzle parts of an aeroengine. The components were subjected to rapid thermal transients during long accelerated endurance testing, equivalent to 1000 h of engine operations. The coatings also withstood the gas erosion of supersonic combustion products, vibratory loads of 4 g and more than 30000 nozzle actuations similar to aircraft maneuver. The paper also presents a brief review of implications of a nano-structured thermal barrier coating and certain nuances of chemical synthesis which forms the backbone of the strategies for durable coatings.
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