Isothermal aging characteristics of rare earth magnesium hexaaluminate based advanced thermal barrier coatings

¹Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur 721302, India

²Electro Minerals Division, Carborundum Universal Limited, Kochi 683109, India

³Industrial Ceramics Division, Carborundum Universal Limited, Hosur 635126, India

Adv. Mater. Lett., 2018, 9 (5), pp 375-382

DOI: 10.5185/amlett.2018.1674

Publication Date (Web): May 17, 2018

Copyright © IAAM-VBRI Press

E-mail: k_biswas@metal.iitkgp.ernet.in

Abstract

The isothermal aging characteristics of rare earth magnesium hexaaluminate (REMHA) based thermal barrier coatings (TBC) such as lanthanum magnesium hexaaluminates (LMHA), Neodymium doped LMHA (LNMHA) and LNMHA-Yttrium aluminium garnet (YAG) composite were evaluated at 1400 °C and compared with standard yttria stabilized zirconia (YSZ) coating. The platelet structure of hexaaluminate forms meso-porous structure and provides superior sintering resistance than YSZ coating. Faster grain growth kinetics is observed in YSZ coating as compared to hexaaluminate-based coatings. As a result, the mechanical properties of YSZ coating deteriorate severely whereas hexaaluminate based coating remains almost unaltered. The LNMHA coating is found to be the best sintering resistance among them. LNMHA and LNMHA-YAG composite have potential to meet the requirement of advanced TBC operating even at 1400 °C. 

Keywords

Grain growth, microstructure-final, platelet, mechanical properties, isothermal ageing.