Effect of bilayer period on structural and mechanical properties of nanocomposite TiAlN/MoN multilayer films synthesized by cathodic arc ion-plating

Abstract

TiAlN/MoN multilayers were deposited on Si (100) and cemented carbide substrates using TiAl and Mo targets in a cathodic arc ion plating system with 1-fold rotation. The bilayer thickness (Λ) of all the layers was controlled via rotational speed of substrate holder within a rage of 21 to 124nm. The TiAlN/MoN has a multilayered structure in which nano-crystalline TiAlN layers alternate with the nano-crystalline MoN layers. The Ti:Al ratios measured by EDS over all samples were closed to the designed ratio and corresponded to Ti0.70Al0.30N composition. TiAlN/MoN nanoscale multilayer thin films exhibited a TiAlN (200), TiAlN (220), MoN (202) and MoN (200) crystalline orientation. The highest hardness and Young's modulus were obtained with a bilayer period of 25nm, while wear rate decreased with decreasing bilayer period. On average, nanoindentation measurements combined with atomic force microscopy (AFM) and cross-sectional scanning electron microscopy (SEM) revealed improved mechanical properties of TiAlN/MoN films with decreasing bilayer period were attributed to their densified microstructure with development of fine grains and reduced surface roughness.