Nanophase Hardfacing New Possibilities for Functional Surfaces

Abstract

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.