Ti-Impfen von Ni-Basisloten zur Steigerung der Präzision im Lötgut

• Ti inoculation of Ni based brazing alloys to increase the precision in the filler metal

Hebing, Julian; Bobzin, Kirsten (Thesis advisor); Reisgen, Uwe (Thesis advisor)

Düren : Shaker Verlag (2022)
Book, Dissertation / PhD Thesis

In: Schriftenreihe Oberflächentechnik 72
Page(s)/Article-Nr.: VII, 149 Seiten, Seite A-R : Illustrationen, Diagramme

Dissertation, RWTH Aachen University, 2022

Abstract

Nickel-based brazing alloys are widely used and will continue to occupy an important role in joining technology in the future. In particular, these brazing alloys have always been used for components that are exposed to high thermal and corrosive stress during operation. However, due to the melting-point-lowering metalloids such as silicon, phosphorus and boron contained in these brazing alloys, the formation of hard and brittle phases or brittle phase bands occurs in the center of the brazed joint during the brazing process, which is associated with deteriorated and unpredictable mechanical properties of the joint. Common approaches to avoiding or dissolving these brittle phases are based on concentration equalization or the distribution of metalloids in the brazing gap and base material via diffusion processes. These approaches are characterized by lengthy holding times, high temperatures or even extensive technical efforts to limit the brazing gap width and the associated shortening of the diffusion paths. The resulting high technical effort, the lengthy process times, the high brazing temperatures and the high energy demand limit the economic efficiency of these brazing processes without the reliable reproducibility of the joint properties. This work investigates and further develops the new method of inoculating nickel-based brazing alloys. Various Ti-inoculated brazing pastes as well as amorphous brazing foils made from the brazing alloys Ni 620, Ni 650 and Ni 660 are produced, tested and characterized on industrially typical brazed joints made of hot work tool steel or stainless steel. Inoculation enables the targeted formation of Ti-containing precipitates within the brazing gap which change the microstructure of the joint. In contrast to existing approaches, the brittle phases are made smaller by the precipitates and distributed in the brazing material. The investigations demonstrate that this approach is well suited to significantly improve the mechanical properties of nickel-based brazing joints even in short brazing processes and, in particular, to increase the reproducibility of the joint properties.

Institutions

• Chair of Surface Engineering [419010]