Special Issue Paper
(Received 11 April 2016; accepted 11 May 2016)
Published Online: 22 December 2016
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Low temperature surface engineering of stainless steels by dissolving large quantities of nitrogen and carbon has become a favorable technological process. Such treatments usually yield the so-called expanded austenite, which is a super-saturated diffusion zone and can be produced by a salt, gas, or plasma-based processes. The present manuscript addressed the production of expanded austenite on a superaustenitic stainless steel at low temperature. Gas mixtures with nitrogen or both nitrogen and carbon bearing gases were applied in a plasma atmosphere at 400°C for 5 h. Microstructural characterization was conducted applying light optical microscopy, X-ray diffraction, and transmission electron microscopy. In addition, microhardness measurements were performed at the surface of the samples. Plasma nitriding and nitrocarburising at 400°C resulted in a homogeneous case composed solely by expanded austenite as detected by X-ray diffraction. Similar microhardness was observed for both processes, whereas nitrocarburising provided a thicker diffusion zone when compared to nitriding. Fine iron-chromium nitride precipitation was only identified by transmission electron microscopy (TEM). Selected area electron diffraction yields similar lattice parameters for both processes.
Fernandes, F. A. P.
Center of Engineering, Modelling and Applied Social Sciences, Federal Univ. of ABC (UFABC) - São Bernardo do Campo, São Paulo 09606-070,
Casteletti, L. C.
Department of Materials Engineering, Univ. of São Paulo (USP) - São Carlos, São Paulo,
Department of Mechanical Engineering, São Paulo State Univ. (UNESP) - Ilha Solteira, São Paulo,
Stock #: MPC20160048