In order to determine the suitability of S-phase coatings to be applied as an interlayer improving the adhesion of hard coatings, chromium nitride coatings containing S-phase interlayers with two different nitrogen contents were deposited by reactive magnetron sputtering onto austenitic steel substrates with two different initial states. The microstructure and phase composition of the composite coatings were examined by scanning electron microscopy and X-ray diffraction. In addition, the mechanical properties and adhesion were assessed using the nanoindentation method and scratch test. Use of the S-phase as an interlayer to improve adhesion has been demonstrated, especially for S-phase with higher nitrogen content. Research indicates that during chromium nitride deposition, the formation and mechanical behaviour of the S-phase as an interlayer is significantly influenced by diffusion processes at the interface between the interlayer and the austenitic steel substrate.