Structural and mechanical evaluation of deposited nano structured TiN coating using active screen plasma nitriding technique

¹ Centre of Excellence for High Strength Alloys Technology, School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran 16844, Iran
² Materials Engineering Department, Faculty of Mechanical Engineering, University of Tabriz, Tabriz, Iran

^a e-mail: arash_ya1997@yahoo.com

Received: 19 February 2013
Revised: 19 August 2013
Accepted: 14 January 2014
Published online: 14 February 2014

Abstract

Nano structured TiN coatings were prepared by means of active screen plasma nitriding (ASPN) method at a constant temperature of 550 °C for 5, 7.5 and 10 h under three gas mixtures of H₂:N₂% = 3:1, 1:1 and 1:3. In order to investigate the coating properties such as the chemical composition, surface morphology, surface topography and hardness, several analysis techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and nano indentation were employed. The results indicated that the growth of the TiN film under active screen plasma nitriding deposition had a (2 0 0) preferred orientation. Moreover, it was found that N₂-50%H₂ atmosphere provides the highest deposition rate leading to the maximum roughness and minimum nano hardness values. Similar observation was obtained by increasing the nitriding time. Furthermore, a model was proposed for the relation between the hardness and the surface roughness of the coating in which higher surface roughness leads to lower hardness.