Multiphase-Multifunctional Ceramic Coatings
Final rept. 3 Jun 2010-3 Jun 2013
CENTRO DE INVESTIGACION EN MATERIALES AVANZADOS S C CHIH (MEXICO)
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This project deals with ceramic coatings deposited by thermal spray and based on La2Zr2O7 LZO toughening phase. The phase that showed promising results in dense ceramics to be scaled up and prepare coatings is the LaAlO3 LAO. LZO and LAO mixtures in a 7030 mol ratio were deposited on SS304 and FeCrAlY substrates. Milling followed by a spray drying process enabled production of 70LZO30LAO mixture in the form of spherical agglomerates with adequate size distribution and flow properties for feeding into a thermal-spray system. The as-sprayed coating comprises crystalline LZO and partially amorphous LAO. The amorphous phase resulted from the high cooling rate experienced by the molten particles. The coatings were annealed at 1100 deg C for promoting crystallization of the amorphous phase. The elastic modulus and hardness clearly increased after the annealing treatment. However, the fracture toughness tested on the annealed coating showed low values of 1.04 MPa m. Further research is required to mitigate the formation of amorphous LAO by proper control of the quenching conditions. Although the fracture toughness improves moderately as the LaAlO3 fraction increases in dense ceramics, the values are still lower than those considered acceptable.
- Coatings, Colorants and Finishes