OPTIMIZATION OF DUPLEX COATINGS BUILT FROM NITRIDING AND ION PLATING WITH CONTINUOUS AND DISCONTINUOUS OPERATION FOR CONSTRUCTION AND HOT-WORKING STEELS

Multifunctional coatings combining a nitriding treatment and physical vapour deposition allow the performance of cutting and forging tools t o be boosted, since the improved mechanical support of the coating mak es them withstand higher loads. This treatment can also be used for we ar parts made from construction steels to increase their fatigue and w ear resistance. Hard coatings applied on nitrided layers can replace o r enhance the epsilon or gamma' layers currently used. These treatment s can be made in a discontinuous mode using a dedicated equipment for the nitriding and coating treatment or in a continuous mode, i.e. dire ctly in the coating reactor. These treatments were applied and optimiz ed for a construction steel 35NCD16 and a hot working steel Z38CDV5-1. Coating conditions have a decisive impact on the thermal stability of the iron nitride layers. This aspect was studied in detail and severa l technical solutions have been identified. Finally, it will be shown that in contradiction to previous findings the coatings have only a ne gligible influence on the stress intensity in the nitrided zone.