Protocol for the preparation of alumina/metal brazed joints-Master Thesis MANUEL RAMONES

Author: MANUEL RAMONES ; Type of thesis: Master thesis
Abstract: Brazing is the joining of materials through the use of heat and a filler metal with a melting temperature above 450°C but below the melting point of the metals being joined. This technique joins parts by creating a metallurgical bond between the filler metal and the surfaces of the two materials joined. There are several factors which have direct influence on the final quality of a brazed piece:
the filler metal selection, the heating technique, the atmosphere in which the process is performed, the cleaning procedure, the assembly of pieces, etc. In metal-ceramic junctions, ceramic surfaces, especially oxides, are very stable chemically, consequently, molten metals do not wet them well. There are several techniques that allow to overcome the chemical challenge. In order to develop a procedure that ensures the conditions to achieve a successful brazing process, several techniques for metal-ceramic brazing in a controlled atmosphere (vacuum) were tested. Brazing using active filler metals and direct brazing using ceramic metallization by sputtering were studied in this work. Alumina (Al2O3) was chosen as the ceramic part, whereas stainless steel 304 and Inconel were chosen as metallic components, cylindrical samples were assembled in lap configuration and were heated by IR lamps. The pieces were cut and the cross-section was studied by Scanning Electron Microscope SEM and energy-dispersive X-ray spectroscopy (EDS, EDX) searching for evidence of filler metal uniform spread and diffusion. The samples brazed using Pallabraze 850 disc of 0.01 mm of thickness for braze Inconel and Metallized alumina with 1m of Titanium and using Argon atmosphere showed the more uniform distribution and diffusion.