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Plasma emission spectroscopy as a monitoring tool for deposition of S-phase layers by magnetron sputtering DOI:10.15199/28.2015.5.15

  Numerous attempts to improve hardness and wear resistance of austenitic stainless steel by nitriding led to identification of so called S-phase (expanded austenite). Currently S-phase is obtained not only by nitriding of steel but also by physical vapour deposition (PVD). The aim of present work was to verify whether the magnetron sputter deposition process of the S-phase layers from 316L steel target can be monitored with the use of plasma optical emission spectroscopy (OES). Specific atomic emission lines of steel target and gas atmosphere components were chosen and analyzed. A series of deposition processes as well as samples characterization was performed. The atomic chromium emission line at 520.8 nm has been selected and proven to be sensitive to the 316L target poisoning process and thus appropriate for deposition process monitoring. Key words: expanded austenite, S-phase, optical emission spectroscopy, process control, magnetron sputtering.1. INTRODUCTION S-phase, also called expanded austenite, can be considered as nitrogen or carbon solid solution based on Fe-Cr-Ni austenite. There are several methods to obtain S-phase layers, e.g. gas and plasma nitriding [1, 2] and plasma/ion implantation [3, 4]. There are also reports on deposition of S-phase by reactive magnetron sputtering [5, 6]. S-phase has a fcc-type structure with a kind of tetragonalisation observed. The magnetic permeability studies suggest that it can be treated as a separate phase, especially when nitrogen content is relatively high [2, 7]. An analysis of stress-free samples by Christiansen and Somers demonstrated that the S-phase has a fcc structure with stacking faults, deviating the X-ray line profiles from fault free positions [8]. The lattice parameter of S-phase strongly depends on nitrogen content and can change from 0.360 up to 0.405 nm [9]. Kappaganthu and Sun [5] concluded that with increasing nitrog[...]

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