Papers by Keyword: Interfacial Characterization

Abstract: Robust bonding and integration technologies are critically needed for the successful implementation of silicon carbide based components and systems in a wide variety of aerospace and ground based applications. These technologies include bonding of silicon carbide to silicon carbide as well as silicon carbide to metallic systems. A diffusion bonding based approach has been utilized for joining of silicon carbide (SiC) to silicon carbide sub-elements for a micro-electro-mechanical systems lean direct injector (MEMS LDI) application. The objective is to join SiC sub-elements to from a leak-free injector that has complex internal passages for the flow and mixing of fuel and air. A previous bonding approach relied upon silica glass-based interlayers that were non-uniform and not leak free. In the newly developed joining approach, titanium foils and physically vapor deposited titanium coatings were used to form diffusion bonds between SiC materials using hot pressing. Microscopy results show the formation of well adhered diffusion bonds. Initial tests show that the bond strength is much higher than required for the component system. Benefits of the joining technology are fabrication of leak free joints with high temperature and mechanical capability.

Abstract: Tungsten has the highest melting point among all metal, which makes it withstand thermal shock and erosion in high temperature environments. In this study, Tungsten coatings were sprayed onto the oxygen-free copper substrates by plasma spraying using inert gases protection. XRD, SEM and EDS were used to identify the phases, morphologies and compositions of the coatings. Vickers micro-hardness and bonding strength of the tungsten coatings were also measured. The results revealed that the hardness distribution of the tungsten coatings was different along the thickness direction. The tungsten coating without any interlayer showed higher bonding strength than that of the other two coatings with NiCrAl and W/Cu interlayers, respectively.