The influence of nitrogen concentration on the microstructure, chemical and electronic properties of Fe-N thin films and their tribological behaviour are studied. Increasing the nitrogen concentration from 5% to 12%, results in the decrease in friction coefficient from 0.14 to 0.04, while wear life increases significantly. However, increase in nitrogen concentration to 32% results in the increase in friction coefficient to 0.1 and decrease in wear life. Therefore, lowest friction and longest wear life is observed in the film with 12% nitrogen, which is due to the formation of epsilon-Fe2N phase having high bond strength and chemically passive surface. (c) 2014 Elsevier Ltd. All rights reserved.