High safety and low weight are requested for modern automobiles. Both demands are met best by tailored application of different materials. Multimaterial car body design is a challenge for joining and welding.

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This paper demonstrates the possibility of producing iron-or chromium-based nanophase hardfaced coatings by means of common arc welding methods (TIG, PTA). The appropriate composition of the alloys to be deposited allows to control the structural properties and thus also the coating properties of the weld metal. Specific variations of the alloying elements allow also the realisation of a nanostructured solidification of the carbides and borides with cooling rates that are common for arc surfacing processes. The hardfaced coatings, which had been thus produced, showed phase dimensions of approximately 100 -300 nm. Based on the results it is established that the influence of the surfacing parameters and of the coating thickness and thus the influence of the heat control on the nanostructuring process is, compared with the influence of the alloy composition, of secondary importance. The generation of nanoscale structures in hardfaced coatings allows the improvement of mechanical properties, wear resistance and corrosion resistance. Potential applications for these types of hardfaced coatings lie, in particular, in the field of cutting tools that are exposed to corrosion and wear.

During the last years, materials science has focused more and more on the development of nanomaterials. Reasons for that are the enormous advantages these materials can offer for various applications as their special structure yields the improvement of the material properties, such as hardness, strength and ductility. However, the production of especially “massive” nanomaterials is quite complex. The present study demonstrates the possibility of producing iron- or chromium-based nanophase hardfaced coatings with a thickness of several millimetres by means of common arc welding methods (TIG, PTA). An appropriate alloy composition allows to control the structural properties of the solidifying weld metal. Specific variations of the alloying elements enable the realisation of a nanostructured solidification of the carbides and/or borides with cooling rates that are common for arc surfacing processes. In the hardfaced coatings phase dimensions of approximately 100-300 nm were achieved. Based on the results it is established that the influence of the surfacing parameters and of the coating thickness and thus the influence of the heat control on the nanostructuring process is, compared with the influence of the alloy composition, of secondary importance. Several tests showed that the generation of nanoscale structures in the hardfaced coatings allows the improvement of mechanical properties, wear resistance and corrosion resistance. Potential applications for these types of hardfaced coatings lie, in particular, in the field of cutting tools that are exposed to corrosion and wear.

Schlüsselwörter: MSG-Schweißen / Stahl / Aluminium / Mischverbindung / Werkstoffkombination / In recent years, the vehicle weight has been constantly increased due to particular requirements made on the passenger safety and comfort. For maintaining or even improving the road performance, engine manufacturers have been forced to supply increasingly more efficient combustion motors. However, increased exhaust emmission is a consequence. The requirements made on environmental protection, however, demand that the vehicle weight is reduced again in future. New material concepts will be required for the implementation. One possibility is the Multi-Material construction where different materials are combined. Thus, the locally optimized exploitation of the material-specific properties is guaranteed and a design which is appropriate to the type of duty is created. The combination of steel with aluminium has the highest relevance. Since the final contour of the components is often produced by a reforming process, also forming aspects must be taken into account, besides the consideration of sufficient static strength. The development of modern, digitally controlled arc welding processes has, in recent years, allowed for the reliable, reproducible joining of steel-aluminium mixed compounds. Investigations about the joining of steel with aluminium, using different arc welding processes, are carried out in the Weldin and Joining Institute (ISF) RWTH Aachen University. Special attention is given to the possibility of later forming of the joints.