Molybdenum

Identify the material and product route

Elmet lists weak oxidation beginning at 300°C in air or oxygen and rapid oxidation to MoO₃ at 600°C. Its table separately lists nitriding above 1500°C in nitrogen and carburization above 900°C in hydrocarbons. These are screening observations. Establish atmosphere, duration and acceptable material loss for the actual service. Elmet molybdenum reactions

Molybdenum, symbol Mo, is a refractory metal supplied as powder, billet and worked mill products. Elmet's pure-metal product sheet covers rod, wire, plate, sheet and foil with Mo ≥99.95% and individual impurity limits. That description is distinct from an unspecified “moly” component or a molybdenum-containing steel. Elmet pure molybdenum product sheet

Pure Mo, TZM and lanthanated molybdenum are separate purchasing choices. Elmet's TZM rod sheet specifies titanium 0.4–0.55%, zirconium 0.06–0.12% and carbon 100–400 ppm, and identifies high-temperature strength and creep resistance among its uses. Do not transfer TZM performance to pure molybdenum merely because both products are used in furnaces. Elmet TZM rod sheet

Certification and condition matter

Elmet's legacy pure-mill-product sheet explicitly says that chemistry complies with ASTM powder-lot requirements, while finished-part chemical analysis and mechanical properties are not routinely evaluated per ASTM requirements. It cites B387-90, reapproved 1995, for rod/wire and B386-91, reapproved 1997, for flat products as process-control guidelines. These historical references do not certify a new order to current ASTM editions. Elmet scope statement

Elmet separately publishes a pressed-and-sintered pure-molybdenum billet specification, PD-7010, Issue 1 dated 2009-08-10. It calls for shipment identification and a certification report covering relevant chemical, mechanical, structural and physical-integrity features. That is a billet-specific documentation provision, not a universal promise for all molybdenum products. Elmet PM billet specification

Mechanical properties depend on working history and the ductile-to-brittle transition. ESPI also describes recrystallization as dependent on prior working and condition; its example of full recrystallization at 1180°C for one hour applies to a 16 mm bar reduced 97% by rolling. It is not a universal annealing schedule or a temperature below which every product is unchanged. ESPI mechanical and fabrication data

Physical properties and useful units

Elmet's physical-property sheet gives the following reference values:

These are reference properties, not order-specific guaranteed limits. The resistivity equals 5.52 × 10⁻⁸ Ω·m; the modulus is approximately 317 GPa. Preserve temperature and unit basis when importing values into a calculation. Elmet physical-property sheet

For an ideal 100 × 100 × 1 mm solid plate, volume is 10 cm³ and estimated mass is 102.2 g. This original calculation excludes tolerances, holes and coatings. For a uniform conductor 100 mm long with 1 mm² cross-section at 27°C, R = ρL/A gives 0.00552 Ω. Contact resistance and self-heating are excluded; this is an initial bulk-resistance estimate, not an electrical component rating.

Atmosphere controls the service limit

Elmet's chemical-interaction sheet lists weak oxidation beginning at 300°C in air/oxygen and rapid oxidation to MoO3 at 600°C. It separately lists nitriding beginning above 1500°C in nitrogen and carburization above 900°C in hydrocarbons. These are qualitative producer screening entries, not measured lifetime guarantees or permissible process limits. Elmet chemical interactions

ESPI advises against continued service above 500°C in an oxidizing atmosphere without an adequate protective coating. Its guidance reinforces the need to state atmosphere alongside temperature. ESPI oxidation limitation

Record oxygen, moisture, pressure and gas composition during normal service, warm-up, shutdown and possible leaks.

For liquid or chemical exposure, identify concentration, temperature, oxidizing contaminants and contact duration. Elmet's interaction table distinguishes dilute sulfuric acid at 100°C from concentrated acid at 200°C, and aqueous alkalis from molten alkalis. Avoid reducing those entries to “acid resistant” or “alkali compatible.” Elmet chemical screening table

Fabrication and handling

ESPI identifies surface cleanliness and a closely controlled inert atmosphere for fusion welding, and notes that arc-cast material is preferred over powder-metallurgy product for welding. This is process-selection guidance; it does not qualify a joint or establish a universal welding procedure. ESPI joining guidance

Agree on stock condition and processing sequence before final machining. Use representative trials for thin sections, critical edges, joining and thermal cycles. Define the final surface and inspection requirements, including whether damage or contamination from machining is acceptable for the intended service. Do not substitute a generic refractory-metal cutting recipe for the actual grade and geometry.

Elmet's molybdenum SDS, S-17-002 Rev (−), 03-15-2022, warns against inhaling dust/fumes and identifies fine metal dust as potentially explosive, requiring collection at its source. Bulk parts, powder and generated dust require different process assessments. Obtain the supplied product's current SDS and design extraction, housekeeping and waste handling around the generated form. Elmet molybdenum SDS

Source versions and related reference

The pure-product sheet footer says vd-1/9/06, and the TZM sheet rv-11/30/17, despite newer filenames or upload paths. The inspected physical-property and chemical-interaction sheets and ESPI page show no explicit technical revision date. Their role here is bounded reference guidance; obtain current specifications and order-specific evidence for acceptance.

Grades, tempers and conditions