Molybdenum brazing

A schematic diagram of the power generation test apparatus is shown in Figure 2. The emitter, which was a disc with a diameter of 16 mm and a thickness of 5 mm was joined using ruthenium-molybdenum braze to a support made of tantalum, and was placed facing the molybdenum collector at a distance of 400 im. The emitter was heated to 1400 1900 K by electron bombardment Then the collector was cooled by radiative cooling to about 1000 K. 

Ceramics are joined to metals by metal eoating and brazing, and by the use of adhesives. In metal coating, the mating face of the ceramic part is coated in a thin film of a refractory metal such as molybdenum (usually applied as a powder and then heated). 

Brazing Satisfactory brazed joints in molybdenum have been made using oxyacetylene torch and furnace brazing techniques. 

Silver-palladium-manganese brazes possess excellent creep characteristics and have been developed for high-temperature applications involving the use of cobalt or nickel-based alloys, heat-resistant steels, molybdenum and tungsten. Their liquidus temperatures lie in the range 1 100-1 250°C. 

Pure ruthenium powder or mixed ruthenium-molybdenum powders have been found able to effect good joints between molybdenum and tungsten. A eutectic melting above 1 900°C is formed, and joints produced in hydrogen atmospheres at 2 100°C operate satisfactorily at 1 500°C. A cobalt-palladium-gold alloy has also been reported to be useful in brazing molybdenum. 

Molybdenum boride (Mo B) is used to braze (weld) special metals and for noncorrosive electrical connectors and switches. It is also used to manufacture high-speed cutting tools and noncorrosive, abrasion-resistant parts for machinery. 

Molybdenum pentachloride (MoGl ) is used as a brazing and soldering flux and to make fire-retardant resins. 

Use Brazes to join molybdenum, tungsten, tantalum, and niobium parts, especially electronic components, corrosion and abrasion-resistant parts, cutting tools, refractory cermets. 

Use Chlorination catalyst, vapor-deposited molybdenum coatings, component of fire-retardant resins, brazing and soldering flux, intermediate for organo-metallic compounds, e.g., molybdenum hexacar-bonyl. 

Evidence of strong chemical interaction is seen in ZS/Palco/Cu-clad-Mo joints (Fig. 3a). A multilayer transition zone (Fig. 3a b) separates the ZS from molybdenum. A change in the microstmcture occurs upon traversing from the ZS side through the braze region (Fig. 3b-d) to the braze/Cu-clad-Mo interface (Fig. 3e f) and into the Cu-clad-Mo region (Fig. 3f). The EDS analysis across the joint (Fig. 3b) showed that Co, Cu, Mo and Pd had penetrated within ZS to a... 

Storage Hygroscopic air- and moisture-sensitive Uses Chlorination catalyst vapor-deposited molybdenum coatings component of fire-retardant resins brazing and soldering flux intermediate for organometallic compds., e.g. 

Boric acid Molybdenum pentachloride Potassium fluoborate Trimethyl borate brazing flux, gaseous Tri methyl borate bread improver mfg. 

The original conductor materials were stainless steel or platinum. These materials were later replaced with more corrosion-resistant alloys with improved fatigue resistance such as MP35N (SPS Technologies Cleveland OH), an alloy of nickel, chromium, cobalt, and molybdenum. In order to further reduce the resistance to current flow, specialized conductors were designed, including DBS (drawn brazed strand) and DFT (drawn filled tube)... 

Figure 102. Laminar composite of graphite/AgCuTi braze/TZM molybdenum alloy. Micro-structural imaging by various methods of contrast enhancement.

Active metal brazing (AMB) is a process to braze metals, such as Kovar , titanium, copper, and molybdenum, to ceramics. The process does not require a metallization on the ceramic. For this chapter, only copper brazing will be addressed. The AMB process is used by some manufacturers as an alternative to DBC as it provides higher adhesive strength while using a less critical furnace profile. It also does not rely on oxide formation as in the DBC process. 

Diffusion bonding eliminates any foreign material as needed in brazing so it would be preferred for implantable medical device applications. Alumina can be diffusion bonded to a few biocompatible metals including tungsten, platinum, molybdenum, stainless steel, and niobium [58,61]. Zirconia has been successfully diffusion... 

Welding and brazing. Molybdenum can be joined using conventionally accepted welding techniques except for gas. Heli-arc welding is most common and usually provides satisfactory results. Complex welding operations may require more sophisticated or special techniques. 

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