Abstract The adhesion of plasma-deposited TiN from TiCl 4H 2N 2 gas mixtures on AISI M2 (Werkstoffnr. 1.3343) steel substrates can be improved by proper cleaning of the substrates in a non-corrosive solution such as an aliphatic hydrocarbon (dodecane). From the deposition parameters, such as the substrate temperature, pressure, r.f. power and respective gas flows, the temperature appears to be the most influential parameter for the adhesion. The removal or reduction of metal oxides present on the surface by increasing the substrate temperature and/or in situ plasma etching in H 2 enhances the adhesion, as indicated by the increased critical load L c in a scratch adhesion test. The “cleaned” surface can be made more resistant to the aggressive discharge by treating the surface in an N 2 or N 2H 2 discharge. The nitrides formed on the surface, one of which is Fe 2N, also influence the nucleation and growth mechanism of TiN, which leads to a more random orientation of the TiN crystallites. The residual stress in TiN films, deposited on M2 steel substrates pre-treated in an N 2 discharge, appears to be lower than the stress in TiN films deposited on a steel surface which has not been pre-treated in an N 2 discharge. As a result a substantial improvement is obtained in critical load. Routine L c values of up to 50 N have been obtained for TiN coatings with a thickness of about 4.5 μm.