In this paper the influence of the layer's microstructure on the hardness enhancement in multilayer nanocrystalline films and the oxidation resistance are studied. The TiN/MoxC multilayer films at different modulation period, and MoxC and TiN monolayer films were deposited on the (0 0 1) silicon wafers and molybdenum sheets by rf and dc magnetron sputtering. The monolayer TiN films with a thickness of about 2 mu m are of pure face-center cubic TiN phase, while the monolayer MoxC films consist of two phases, one of which is body-center cubic Mo and the other is hexagonal Mo2C as determined by XRD. The coarse columnar grains of about 200 nm in the monolayer TiN films become much smaller or disappear in the multilayer films. The hardness enhancement of the multilayer films takes place at the modulation period of 320 nm, which can reach to 26 GPa and is much higher than the values of MoxC and TiN monolayer films. This enhancement in hardness can be explained as the decrease in the size and/or disappearance of columnar grains in the TiN layer. The Young's modulus in the temperature range from 100 to 400 degrees C increases with decreasing modulation period. It is found that about 100 nm thick TiN films can increase largely the oxidation resistance of MoxC films. (C) 2006 Elsevier Ltd. All rights reserved.