Wetting and interactions of Ag–Cu–Ti and Ag–Cu–Ni alloys with ceramic and steel substrates for use as sealing materials in a DCFC stack

Abstract

Ag and Ag-based pseudo-alloys were evaluated in terms of application as metal brazes for the use in a hybrid direct carbon fuel cell stack. This paper reports on a series of wetting experiments on systems of pure Ag as well as Ag-Cu-Ti and Ag-Cu-Ni pseudo-alloys in contact with the widely used austenitic stainless steel SS316L, the ferritic steels Crofer22APU and Croffer22H and with polycrystalline partially stabilized zirconia (TZ-3Y) for the determination of the interfacial properties of the above systems. Pure Ag in air showed poor wettability (h [ 90°) with all substrates. The Ag-Cu-Ti pseudo-alloy in vacuum (P = 2.5 9 10 -3 mbar) showed improved wettability, with h & 40°for the steels and h & 50°for the TZ-3Y substrates. The Ag-Cu-Ni pseudo-alloy in air showed excellent wetting properties (h \ 10°) with all the substrates, but its high liquidus temperature makes it unsuitable for use with the SS316L steel. In low vacuum (P = 1.5 9 10 -1 mbar), the contact angle was increased (h & 65°) but the low oxygen concentration limits the oxidation of the steel surface. Selected systems of the pseudo-alloys in contact with steel and TZ-3Y substrates were treated for 120 h in the operating conditions of a hybrid direct carbon fuel cell, in order to evaluate the thermal stability of the joints. Despite the reactions taking place on the interface, the joints showed good stability and no separation of the two phases occurred.

Acoustical Investigation of Adhesion in Liquid Metal–Ceramic Interfaces

“…The adhesion of the metal-ceramic system is the most important factor of all metal bonds. It is determined by the change in the free energies of two materials when they come into contact [16] (Fig. 1).…”

A method for producing ceramic/stainless steel composites by laser welding with calculation optimisation

“…As shown in Figure 2(b), the filler had good wettability with both SS and Al 2 O 3 , and no cracks formed in the brazed weld. This is due to the addition of chemically active Ti element to the filler alloy improves its wettability to the ceramic substrate [44]. The AgCuTi filler metal exhibited good wettability, and it reacted with SS and Al 2 O 3 .…”

Progress in Improving Joint Strength of Brazed Cemented Carbides and Steels

“…Although BAg22 and BAg24 are the most popular filler alloys for brazing cemented carbides to steels, alloying addition to these filler alloys presents new opportunities for enhancing the joint strength. Each of the alloying elements in the braze serve a particular function in improving the joint strength: Cu and Ag serve the purpose of reducing the residual stress levels generated during the brazing process due to their inherently higher ductility [81, 82]. Co decreases the concentration gradient across WC-Co and braze.…”

“…Cu and Ag serve the purpose of reducing the residual stress levels generated during the brazing process due to their inherently higher ductility [81, 82].…”