Ti1-xSixCyN1-y films have been deposited by reactive cathodic arc evaporation onto cemented carbide substrates. The films were characterized by X-ray diffraction, elastic recoil detection analysis, transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron-energy loss spectroscopy and nanoindentation. Reactive arc evaporation in a mixed CH4 and N-2 gas gave films with 0 <= x <= 0.13 and 0 <= y <= 0.27. All films had the NaCl-structure with a dense columnar microstructure, containing a featherlike pattern of nanocrystalline grains for high Si and C contents. The film hardness was 32-40 GPa. Films with x>0 and y>0 exhibited age-hardening up to 35-44 GPa when isothermally annealed up to 900 degrees C. The temperature threshold for over-ageing was decreased to 700 degrees C with increasing C and Si content, due to migration of Co, W and Cr from the substrate to the film, and loss of Si. The diffusion pathway was tied to grain boundaries provided by the featherlike substructure. (C) 2010 Elsevier B.V. All rights reserved.