Molybdenum has a high melting temperature (2610ˇăC)and it is impractical to transform it into ingot forms by conventional furnace melting techniques. Its manufacture by powder metallurgy consists of three distinct phases: the decomposition of the ore and its reduction to pure metal powder, the pressing of this powder into bars and the sintering of these bars into solid ingots and the swaging, rolling or drawing of these ingots into desired forms and sizes. Some products are fabricated from arc-cast ingots. Prefabricated or continuously compacted and sintered electrodes made from metal powder are arc-melted in a water-cooled copper mold. The process is usually carried out in a vacuum, although in some instances inert-atmosphere melting is employed
In addition to pure molybdenum H Cross Company also produces materials from 50/50 Molybdenum Rhenium Alloy and TZM Molybdenum Alloy:
This alloy offers the strength of molybdenum with the ductility and weldability of rhenium. It is a more expensive alloy and it is available in a limited size ranges. It offers significant advantages in thin foil applications for high temperature delicate parts, especially those that must be welded. Note that, although this alloy is nominally 48% rhenium, it is customarily referred to 50/50 moly/rhenium. In addition to foil this material can also be made in wire and rod form from .005" to .250".
Molybdenum's prime alloy is TZM. This alloy contains 99% Mo, 0.5% Ti and 0.08% Zr. TZM offers twice the strength of pure molybdenum at temperatures over 1300ˇăC. The recrystallization temperature of TZM is approximately 250ˇăC higher than molybdenum and it offers better weldability than pure molybdenum.
TZM's finer grain structure and the formation of TiC and ZrC in the grain boundaries inhibit grain growth and the related failure of the base metal as a result of fracturing along grain boundaries. This characteristic also gives it better properties for welding. TZM generally costs around 25% more than pure molybdenum but in high heat and strength applications it can be well worth the cost differential.
TZM is generally available in sheet and foil in the same size ranges as pure moly with the exception of very thin foil