The influence of an energetic ion bombardment on the microstructure, hardness and thermal stability of hard coatings on the basis of Ti-Al-N and Cr-Al-N is investigated using X-ray diffraction, transmission electron microscopy and nanoindentation. The focus of this work is laid on Ti1-x Alx N coatings with different Al content and Ti-Al-N/Al-Ti-(Ru)-N multilayer coatings with varying concentration of Ru as doping element that were deposited by cathodic arc evaporation at different bias voltages. The impact of the bias voltage on the phase composition, residual stress, crystallite size and hardness is analysed and discussed. The formation of partial coherent interfaces between face centred cubic (fcc) (Ti,Al)N and wurtzitic Al N is studied in detail. The microstructural changes due to a thermal treatment are investigated in situ and ex situ. The kinetics of the decomposition process of the metastable fcc-(Ti,Al)N phase is correlated with the initial microstructure that was designed by an energetic ion bombardment. The potential for a specific material design of hard coatings by means of energetic treatment and alloying is shown.