Korrosionsschutz durch Auftragschweißen mit den reaktiven Metallen Titan,Tantal und Zirkonium

Corrosion protection using surface-welded titanium, tantalum and zirconium claddings Very stringent demands are imposed on the corrosion resistance properties of components, apparatus, and plants of the chemical industry as well as in apparatus and machine construction. For technical and economic reasons, composite-layer materials which withstand the mechanical and corrosive conditions are employed. The special-purpose metals, titanium, tantalum, and zirconium exhibit high resistance to corrosion by many aggressive media, even at high pressure and temperature; these properties are not achieved by any of the conventional corrosion-resistant materials under the same conditions. The object of the research work was to develop a basis for producing claddings of titanium, tantalum, and zirconium by weld surfacing on a base metal of different composition with the application of the PHS method. Within the scope of the present project, single-layer claddings were applied by PHS weld surfacing with the use of titanium, tantalum, and zirconium of high purity as cladding materials on intermediate layers of nickel and copper, or alloys of these plasma hot wire weld surfacing, titanium, tantalum, zirconium, dilution, intermetallic phases, bonding, ductility elements. Boiler plate HI1 was employed as substrate for the three-layer composite materials. The titanium claddings thus applied have been thoroughly examined by metallographic techniques, layer analysis, and corrosion chemistry. The results indicate the possibility of producing corrosion-resistant claddings of titanium by the PHS method, provided that the welding process is shielded against contamination by atmospheric gases, and the formation of undesirable reaction products in the bonding zone between the base metal and filler material is minimized by means of an intermediate layer. The corrosion resistance of the surface-welded titanium claddings on an intermediate nickel layer coincides extensively with that of the reference material. On the basis of the corrosion analyses, the surface-welded titanium cladding on an intermediate copper layer is not resistant to corrosion. The results of weld surfacing with titanium have been applied to heterogeneous PHS weld surfacing with the special purpose metals tantalum and zirconium. In principle, metallographic examinations verify the possibility of producing a flawless bond between a cladding of zirconium and an intermediate nickel layer. In comparison with the filler material, Zr 702, however, the zirconium claddings applied by PHS weld surfacing exhibit a considerably greater hardness and low ductility. Because of the large difference between the melting points of tantalum and the substrate material, claddings of this kind cannot be reproducibly manufactured with sufficient quality by the PHS method, since the necessary parameters are at the extreme limit of the feasible range as far as the heat transfer is concerned.