Synthesis and Characterization of an Fe/Co Ferrite Spinel Oxide Film Produced by Using N2/Steam Heat Treatment on Two Maraging Steels

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 53; no. 4; pp. 1276 - 1293
• Main Authors: Florez, Mauro Andres Cerra, Ribas, Gemma Fargas, Rovira, Joan Josep Roa, García, Antonio Manuel Mateo, da Mata, Stephany Aparecida Santos, Rodríguez-Castellón, Enrique, da Silva, Marcelo José Gomes
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-04-2022; Springer Nature B.V
• Subjects: Adhesion; Aging; Characterization and Evaluation of Materials; Chemistry and Materials Science; Chipping; Cobalt ferrites; Deformation mechanisms; Engineering; Gases; Heat; Heat treatment; Hematite; Iron oxides; Maraging steels; Materials Science; Metal oxides; Metallic Materials; Molybdenum; Nanotechnology; Nickel; Original Research Article; Oxidation; Oxide coatings; Reaction kinetics; Sliding; Spinel; Steel; Structural Materials; Surfaces and Interfaces; Thin Films; Titanium dioxide; Water vapor
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-022-06588-3

An experimental procedure was developed to obtain an oxide layer formed mainly by spinel on maraging steels. It consists of different stages with specific conditions, such as atmospheres rich in nitrogen and water vapor, and different steps of temperatures and times. Tests were performed on grade 300 and 350 maraging steels. Oxide layer characterization was done using optical and electron microscopy, spectroscopy, X-ray diffraction, and nanoscratch tests in order to determine the adhesion force as well as to observe the main deformation mechanism induced under sliding tests. In both steels, oxide layers are formed by the spinel’s Fe
3
O
4
and CoFe
2
O
4
in amounts close to ca. 85 pct, whereas TiO
2
and MoO
3
represent the other 15 pct. No hematite was found. The low oxygen availability during the heat treatment was fundamental for avoiding hematite formation. A nickel-rich austenitic phase formed at the metal-oxide interface due the kinetics of the oxidation process of the cobalt, iron, and molybdenum. The particular conditions of the heat treatments induced the formation of a mixture of iron, nickel, and cobalt spinel ferrites, thereby contradicting previous studies that said that only magnetite would be formed. The sliding tests at the nanometric length scale highlight that the layer formed on maraging 300 grade presents a better adhesion than the other investigated material due to the fact that it requires more load in order to induce cracks located at the edge of the sliding track and, subsequently, the chipping of the formed layer.
Graphical abstract