H Elmkhah - Department of Materials Engineering, Tarbiat Modares University, Tehran, Iran
A Abdollah-zadeh - Department of Materials Engineering, Tarbiat Modares University, Tehran, Iran
F Mahboubi - Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran, Iran
A.R Sabour Rouhaghdam - Department of Materials Engineering, Tarbiat Modares University, Tehran, Iran

The purpose of this paper is to investigate the relationship between duty cycle and the nucleation and growthmechanism of nanostructured titanium-aluminum nitride (TiAlN) coatings using pulsed-DC plasma-assisted chemicalvapor deposition (PACVD). In order to evaluate the effects of duty cycle, TiAlN coatings were applied for 150 minutein the 30, 40, and 50 % of duty cycle at 470 °C substrate temperature, 10 kHz frequency, and 3 mbar working pressure.The results obtained from SEM, XRD, and EDS tests imply the possibility of homogeneous and heterogeneous nucleationand island-layer growth of the TiAlN coatings. Due to the fact that nucleation and growth occurs in the off-time, thenumber of nuclei significantly increases with decreasing the duty cycle. Consequently, with reducing the duty cycle from50 to 30%, the grain size of the TiAlN coatings decreases from 24 to 14 nm.

nanostructured TiAlN coatings; grain size; duty cycle; PACVD