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Nitrogen Rich Stainless Steel Coatings Obtained by RF Sputtering Process
Claudia Borri, Stefano Caporali, Francesca Borgioli, Emanuele Galvanetto *
1  Department of Industrial Engineering (DIEF), University of Florence, via S. Marta 3, 50139, Florence, Italy


Magnetron sputtering is a useful tool for producing coatings on various substrates at low temperature. The use of an austenitic stainless steel target in a nitrogen-containing plasma mixture allows to obtain nanostructured coatings with the formation of the so-called S phase, supersaturated interstitial solid solution of nitrogen in the expanded and distorted austenite lattice, which shows improved hardness and higher corrosion resistance in comparison with the bulk alloy. In the present research, RF magnetron sputtering deposition of austenitic stainless steel coatings using an AISI 316L target in nitrogen-containing plasma gas was studied. The effect of the N2/Ar gas ratio and the deposition temperature on nitrogen content, phase composition and crystallite size is investigated by mean of XPS, XRD and electron microscopy analyses. The results show that the nitrogen content in the resulting deposit slightly depends on the N2/Ar ratio in the chamber during the deposition, reaching a maximum value of about 35% with a 30% N2/Ar gas composition mixture in the chamber. Data obtained on different substrates are presented and a preliminary evaluation of the corrosion resistance behaviour is also reported.

Keywords: expanded austenite; RF reactive sputtering; nanostructured coatings interstitial solid solution, S phase