Incorporation of zirconia particles into coatings formed on magnesium by plasma electrolytic oxidation

• Published in: Journal of materials science Vol. 43; no. 5; pp. 1532 - 1538
• Main Authors: Arrabal, R., Matykina, E., Skeldon, P., Thompson, G. E.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-03-2008; Springer; Springer Nature B.V
• Subjects: Applied sciences; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Coatings; Cross-disciplinary physics: materials science; rheology; Crystallography and Scattering Methods; Electrolytes; Exact sciences and technology; Magnesium; Magnesium phosphate; Materials Science; Metals. Metallurgy; Nonmetallic coatings; Other topics in materials science; Oxidation; Phases; Phosphates; Physics; Polymer Sciences; Production techniques; Protective coatings; Short circuits; Silicates; Solid Mechanics; Surface treatment; Tetragonal zirconia; Zirconium dioxide; Monoclinic Zirconia; Tetragonal Zirconia; Barrier Film; Zirconia Particle; Plasma Electrolytic Oxidation; Zirconia; Plasma; Surface treatments; Oxidation; Ceramics; Non metal coating
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-007-2360-9

The incorporation of particles of monoclinic zirconia into coatings formed on magnesium by plasma electrolytic oxidation has been examined in order to investigate the mechanism of coating formation. The coatings, developed under DC conditions in alkaline silicate and phosphate electrolytes, comprised two main layers and contained MgO, Mg
2
SiO
4
, and Mg
3
(PO
4
)
2
phases. Zirconia particles were incorporated preferentially into the inner layer regions and at the coating surface. Zirconium was also redistributed in the outer layer coating material, sometimes resulting in a modified microstructure. Due to local heating at the microdischarge sites, particles underwent transformation from monoclinic to tetragonal zirconia, although monoclinic zirconia was also present in the final coating. Mg
2
Zr
5
O
12
was also formed in the coating produced in phosphate electrolyte. The findings suggest that the outer coating material forms at the inner/outer coating interface region and the coating surface, with transport of particles to the former region through short-circuit paths in the outer layer.