Duplex processes consist in applying a treatment, like annealing, carburizing, or nitriding for example, to a plasma sprayed coating in order to improve particular physical characteristics of this coating. Trials of vacuum heat treatment or low pressure carburizing have been performed on APS NiCr coatings, previously sprayed on a steel type 16MnCr5. As a result, densification and adherence of the coating on the substrate have been significantly increased. To a lesser extent, the coating hardness has also gone up. The diffusion of chemical elements have been highlighted by X-ray analysis, showing the creation of a physicochemical bonding at the interface zone.