Friction in near-surface regions of plasma-nitrided and post-oxidized plain steel at various hydrogen contents

Luvison, Caroline; Sonda, V.; Rovani, Ane C.; Cemin, Felipe; Echeverrigaray, Fernando G.; Aguzzoli, César; Crespi, Ângela E.; Amorim, Cintia L.G.; Costa, M.E.H. Maia da; Baumvol, Israel Jacob Rabin; Figueroa, Carlos A.

doi:10.1016/j.vacuum.2011.11.012

Cited by 5 publications

(1 citation statement)

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“…4g, in a condition in which the sample was nitrided for 2 h. To explain the in-depth oxidized magnetite layer, it is suggested that hydrogenous species from the plasma, e.g. OH [11] are electrons carriers which due to their migration capability through grain boundaries, cracks and pores could reach deeper layers, releasing H to avoid formation of hematite via the intermediate reaction Fe:OH [12]; we believe that the OH species stem from the humidity of environmental air. Moreover, we think that nitrogen also plays a catalytic role in the magnetite formation at least if the percentage of nitrogen (≈80%) in the oxygen and nitrogen mixture is taken into account.…”

Section: Resultsmentioning

confidence: 99%

The Corrosion Enhancement due to Plasma Post-Oxidation Subsequent to Plasma Nitriding of a Steel AISI 4140

et al. 2015

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The corrosion enhancement due to plasma post-oxidation subsequent to plasma nitriding of the samples of low alloy annealed steel AISI 4140 was evaluated. The plasma nitriding was carried out at ≈570• C for 1-3 h in an atmosphere of 75% H2 and 25% N2. After this process post-oxidation at ≈450• C in a gas mixture, air and dry air-like was conducted for an hour. The treated samples were characterized using the XRD, SEM, AFM, potentiodynamic polarization and Vickers microhardness tests. The outcome of combined processes showed the presence of ε and γ nitrided phases in the inner compound layer and in the outer one mostly of magnetite phase and barely visible of hematite one without using H2 in the post-oxidation process. Also in these processes, the corrosion potential proved to be lower in the treated specimens than the untreated ones, and the corrosion current decreased up to one order of magnitude when treated in environment air and air-like ambient.

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Section: Resultsmentioning

confidence: 99%