Thermal Spray Deposition, Phase Stability and Mechanical Properties of La2Zr2O7/LaAlO3 Coatings

• Published in: Journal of thermal spray technology Vol. 26; no. 6; pp. 1198 - 1206
• Main Authors: Lozano-Mandujano, D., Poblano-Salas, C. A., Ruiz-Luna, H., Esparza-Esparza, B., Giraldo-Betancur, A. L., Alvarado-Orozco, J. M., Trápaga-Martínez, L. G., Muñoz-Saldaña, J.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-08-2017
• Subjects: Analytical Chemistry; Characterization and Evaluation of Materials; Chemistry and Materials Science; Corrosion and Coatings; Machines; Manufacturing; Materials Science; Peer Reviewed; Processes; Surfaces and Interfaces; Thin Films; Tribology; TBC; pyrochlores; mechanical properties; thermal spray
• ISSN: 1059-9630; 1544-1016
• DOI: 10.1007/s11666-017-0569-y

This paper deals with the deposition of La
2
Zr
2
O
7
(LZO) and LaAlO
3
(LAO) mixtures by air plasma spray (APS). The raw material for thermal spray, single phase LZO and LAO in a 70:30 mol.% ratio mixture was prepared from commercial metallic oxides by high-energy ball milling (HEBM) and high-temperature solid-state reaction. The HEBM synthesis route, followed by a spray-drying process, successfully produced spherical agglomerates with adequate size distribution and powder-flow properties for feeding an APS system. The as-sprayed coating consisted mainly of a crystalline LZO matrix and partially crystalline LAO, which resulted from the high cooling rate experienced by the molten particles as they impact the substrate. The coatings were annealed at 1100 °C to promote recrystallization of the LAO phase. The reduced elastic modulus and hardness, measured by nanoindentation, increased from 124.1 to 174.7 GPa and from 11.3 to 14.4 GPa, respectively, after the annealing treatment. These values are higher than those reported for YSZ coatings; however, the fracture toughness (
K
IC
) of the annealed coating was only 1.04 MPa m
0.5
.