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Study of SiC–nickel alloy bonding for high temperature applications

✍ Scribed by M.L. Hattali; S. Valette; F. Ropital; G. Stremsdoerfer; N. Mesrati; D. Tréheux


Publisher
Elsevier Science
Year
2009
Tongue
English
Weight
947 KB
Volume
29
Category
Article
ISSN
0955-2219

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✦ Synopsis


We have studied the formation of metal/ceramic joints by solid state bonding technique for applications at temperatures >600 • C. The bonding is obtained between silicon carbide (SiC) and Ni-based super-alloy (HAYNES ® 214 TM ) via metallic foils (Ni, Ag). In some cases a thin coating on the ceramic or the alloy by the electroless JetMétal TM process has been used. Often used in brazing, nickel, when added to silicon carbide, usually give silicides. These reactions yield the "Pest Effect" ("pesting") that induces a catastrophic brittleness of this type of assembling. To minimize the reaction of these metals with silicon carbide, addition of elements limiting the "Pest Effect" on the one hand and, diffusion barriers on the other hand, have been performed. Indeed, the choice of the thin Ni 0.93 B 0.07 coating is based on the ability of boron of improving the mechanical properties of silicides, thus avoiding the "Pest Effect". However, we demonstrate that boron does not allow one to suppress the joint brittleness. Another new joining method employing a thin Ag coating or a Ag foil was tested. This process revealed the absence of chemical reaction at the Ag/SiC interface, thus proving the beneficial role of silver, which acts as an effective diffusion barrier for nickel beyond a certain thickness. This method has led to fabrication of joints presenting high shear resistance (>40 MPa).


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