The increasing interest in lightweight solid oxide fuel cell (SOFC) systems for mobile applications has raised the awareness for questions concerning mechanical robustness of sealing materials in thermo‐cyclic operation. In the planar SOFC design considered in the current work, a metallic silver based braze sealant is used. Although, these rather ductile metallic seals are considered to have advantages compared to brittle glass ceramics under thermal cycling conditions, the behavior of such sealant materials after application relevant thermal cyclic operation has not been reported so far. Hence, the post‐operational characterization of a series of silver braze sealed stacks operated isothermally and under thermal cycling conditions is reported with particular emphasis on the braze morphology. The stacks were disassembled after operation, specimens were extracted in various characteristic positions, and metallographically prepared cross‐sections were analyzed by optical and electron microscopy. It was observed that micro‐pores were formed in the sealant that terminated stack operation, and that the extent of this porosity depended on the actual operation conditions leading eventually to leakage and in some cases even to melting effects. The discussion of the results focuses on the influence of different operation conditions on the damage progress and failure of silver based braze joints.

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Der Einfluss der Größen Substratrauheit und Spritzpartikelgröße auf die Haftung thermisch gespritzter Schichten wurde systematisch untersucht. Neben gängigen Spritzwerkstoffen (Cr 2 O 3 , WCCo, NiCr) und Spritzverfahren (Atmosphärisches Plasmaspritzen (APS) und Hochgeschwindigkeitsflammspritzen (HVOF)) wurden bei den Untersuchungen auch verschiedene Substratwerkstoffe (Stahl, Edelstahl, Aluminium) berücksichtigt.Schlüsselworte: Thermisches Spritzen, Haftung, Substratrauheit, Vorbehandlung, SpritzpartikelgrößeThe influence of substrate roughness and spray particle size on the adhesion of thermal spray coatings was researched systematically. In addition to established spray materials (Cr 2 O 3 , WCCo, NiCr) and spraying processes (atmospheric plasma spraying (APS), high velocity flame spraying (HVOF)) different substrate materials (steel, stainless steel, aluminum) were included in the research work as well.

Within a research project the spray materials Cr 2 O 3 , Cr 3 C 2 NiCr and WCCoCr were considered. Process parameters were determined, optimized and validated allowing the application of very fine spray material fractions (< 25 lm) with plasma and high velocity oxy-fuel spray systems. In addition to improved coating properties like low porosity and improved corrosion resistance the application of near net shape coatings was enabled. The subsequent reduced effort for after-treatment of the coatings can contribute to further rationalization of thermal spray processes.