DIRECT COMBINATION OF PLASMA NITRIDING AND PVD HARDCOATING BY A CONTINUOUS PROCESS

The properties obtained by the combination of nitriding with hardcoating allows a function sharing among core material, hardened case and surface. Such combined properties are of interest for the application in complex stressed tools and machine components. The precondition of a succesful combination of nitrided steels with a hardcoating is especially the compatibility of the structure and the properties of the nitrided layer and the coating. but also the technological and economic aspects of the production of such composites. For example, a discontinuous combination of nitriding and hardcoating has some disadvantages, if no external intermediate treatment is provided. A commercial ion-plating equipment (TINA 900) was modified to realize a continuous process of pulse plasma nitriding and TiN hardcoating in one and the same equipment on various steel grades. Special consideration was given to the investigation of the composite properties such as adhesion, structure, hardness and residual stress as well as the tribological behaviour in dependence on the process parameters. The results of the plasma nitriding in the modified cold-wall reactor are comparable to those of nitriding in a hot-wall plant. The hardness and wear resistance increases. The hardcoating of the nitrided substrates leads to an increased adhesion by deposition of a thin Ti or Ti-TiNx intermediate layer.