INCREASING THE WEAR-RESISTANCE OF FERROUS MATERIALS BY MEANS OF DUPLEX SURFACE-LAYER TECHNIQUES

Objective. Conventional surface engineering help considerably to adapt the service properties of steels to specific user requirements. They have their limitations, however, from the viewpoint of both the surfac e layer properties and of the behaviour of the substrate when exposure conditions become complex, such as wear combined with corrosion, slid ing wear and contact fatigue, etc. The present article sets out to sho w that duplex surface engineering open up further possibilities in thi s respect. Summ. Criteria for suitable layer structures are derived, t aking as a starting point the complex tribological demands placed on t he surface layer of tools and machinery components. Depending on the a pplication, it is necessary to produce more or less thick layers that, where appropriate, require support and/or a postheat treatment. In ma ny instances a combination of surface layer and intermediate layer is required, in which case these can be differently composed and structur ed. Effective duplex surface engineering include the combinations of n itriding and coating with carbide tool material, thermal spraying and nitriding, and duplex treatment using beam-assisted technologies. They open up new possibilities for optimising the properties of ferrous ma terials, particularly in regard to the wear and corrosion behaviour un der different exposure conditions.