1-mu m-thick self-lubricating CrN-Ag composite coatings containing 16 at.% Ag were deposited on Si substrates by reactive co-sputtering at T-s=400 degrees C, and were covered with CrN cap layers with a columnar microstructure and a thickness d=0-1000 nm. Vacuum annealing at T-a=500 and 600 degrees C for 1 h causes Ag transport to the sample surface and the formation of Ag surface grains. Quantitative scanning electron microscopy and energy dispersive spectroscopy analyses show that increasing d from 0 to 10 to 100 nm for T-a=500 degrees C leads to a decrease in the areal density of Ag surface grains from 0.86 to 0.45 to 0.04 mu m(-2), while their lateral size remains constant at 360 +/- 60 nm. However, increasing T-a to 600 degrees C causes a doubling of the Ag grain size, and a 4-30 times larger overall Ag transport. These results are explained by kinetic barriers for Ag diffusion through the porous cap layer with a porosity that decreases with increasing d, resulting in an effective activation barrier for Ag transport that increases from 0.78 eV in the absence of a cap layer to 0.89 eV for d=10 nm and 1.07 eV for d=30 nm. Auger electron spectroscopy depth profile analyses of annealed layers reveal no detectable Ag within the CrN cap layer and a uniform depletion of the Ag reservoir throughout the composite coating thickness, indicating unhindered Ag transport within the composite. The overall results show that a CrN diffusion barrier cap layer is an effective approach to control Ag lubricant transport to the surface of CrN-Ag composite coatings. (C) 2012 Elsevier B. V. All rights reserved.