Tetragonal ZrO2 phase stabilization in coating layers prepared on Zr–2.5%Nb alloy during plasma electrolytic oxidation in sodium aluminate electrolytes. (7th September 2017)

• Record Type: Journal Article
• Authors: Malinovschi, V; Marin, A; Negrea, D; Andrei, V; Coaca, E
• Is Part Of: Materials research express. Volume 4:Number 9(2017)
• Publication Date: 2017-09-07
• Subjects: plasma electrolytic oxidation -- tetragonal ZrO2 phase stabilization -- Zr–2.5%Nb -- sodium aluminate -- anticorrosion coatings; Materials science -- Research -- Periodicals; Materials science -- Periodicals; 620.11
• DOI: 10.1088/2053-1591/aa87c9
• Languages: English
• ISSNs: 2053-1591

Abstract

Abstract: Layers containing polycrystalline zirconia and amorphous aluminum oxide were obtained by plasma electrolytic oxidation (PEO) of Zr–2.5%Nb alloy in aqueous electrolyte solutions comprising NaAlO2 (pH = 13.0), NaAlO2 and NaOH (pH = 13.2), respectively. The PEO coatings were analyzed by x-ray diffraction (XRD), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and potentiodynamic polarization tests. The deposited coating layers contain mainly tetragonal ZrO2 polycrystalline phase and amorphous aluminum oxide (Al2 O3 ) phase. They have thicknesses between 9.0 and 53.0 µ m and are uneven, heterogeneous and porous. Zirconia tetragonal phase stabilization by the aluminum oxide matrix was achieved through the 'constraint' mechanism. The corrosion current density values for the PEO layers are lower by 1–2 orders of magnitude than those of the untreated Zr–2.5%Nb alloy.