ZrN(1.20)/Zr(0) (44)Al(0.56)N(1) (20) multilayer films as well as ZrN(1) (17) and Zr(0 44)Al(0) (56)N(1.20) films were deposited by reactive arc evaporation on WC-Co substrates Samples were post-deposition annealed for 2 h at 800-1200 C As-deposited and heat treated films were characterized by scanning transmission electron microscopy X-ray diffraction and nanoindentation The thermal stability was studied using a combination of differential scanning calorimetry thermogravimetry and mass spectrometry The as-deposited Zr(0 44)Al(0 56)N(1.20) film exhibits a nanocomposite structure of cubic and wurtzite ZrAlN During annealing the formation of ZrN- and AlN-rich domains results in age hardening of both the Zr(0 44)Al(0.56)N(1.20) and the ZrN/ZrAlN multilayers The age hardening is enhanced in the ZrN/ZrAlN multilayer due to straining of the ZrAlN sublayers in which a maximum hardness of 31 GPa is obtained after annealing at 1100 degrees C (C) 2010 Elsevier B V All rights reserved