Molybdenum (Mo)
A refractory metal, melting point about 2620 °C
Typical values for the temper in the title
Molybdenum melts at about 2620 °C and keeps strength at temperatures where steels and nickel alloys already fail. It has a high elastic modulus (about 330 GPa), low expansion and good thermal conductivity, and is much lighter than tungsten (density about 10.2 g/cm³).
Its main weakness is oxidation: in air above about 400–600 °C a volatile oxide forms and the material is consumed. So when hot it is used mainly in vacuum or protective atmospheres: heating elements and shields in vacuum furnaces, glass-melting electrodes, heat spreaders in electronics and sputtering targets. The TZM alloy (with titanium and zirconium) is stronger when hot.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 700 MPa | |
| Yield strength Rp0.2 | 560 MPa | |
| Elongation A | 25% | |
| Hardness | 230 HB | |
| Modulus of elasticity E | 329 GPa | |
| Density ρ | 10.22 g/cm³ | |
| Melting point | about 2620 °C | |
| Machinability | 25% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| Mo molybdenum | min about 99.95 (commercially pure) |
Typical purity for pure molybdenum. Alloys such as TZM contain small Ti, Zr and C additions.
Conditions and product forms
Refractory metals are supplied mainly stress relieved or recrystallized. Properties depend strongly on the production route (powder metallurgy, arc melting) and the amount of working.
| Condition | Properties | When to choose it |
|---|---|---|
| Stress relieved | higher strength, reasonable ductility | most uses |
| Recrystallized | softer, and may be more brittle at room temperature | as required |
Applications
- Heating elements and shields in vacuum furnaces
- Glass-melting electrodes
- Heat spreaders in electronics
- Sputtering targets
- Hot-work tooling
Fabrication
Oxidation
In hot air it oxidizes fast. At high temperatures it is used in vacuum, inert gas or hydrogen, or protected by a coating.
Machining
Possible, with sharp tools and care: at room temperature molybdenum may be brittle and chip at edges.
Welding
By electron beam or laser, with full shielding. The weld zone may be brittle.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| Tungsten (W) | 980–1510 / 760–1170 MPa | Electron beam / TIG with care | higher melting point, about twice as heavy · material page |
| Tantalum (Ta) | 270 / 170 MPa | Electron beam | ductile and highly corrosion resistant · material page |
| Inconel 600 | 550-690 / 170-345 MPa | Good | a nickel alloy for heat in air · material page |
Common mistakes
Using molybdenum hot in air
It oxidizes and is consumed. For heat in air, a nickel alloy or coated molybdenum.
Cold bending to a sharp radius
It may crack. Bend with moderate heating.
Assuming it is as heavy as tungsten
Its density is about half that of tungsten.
Equivalents, standards and supply
| ASTM | B386 |
|---|---|
| Standards | ASTM B386 / ASTM B387 |
| Forms | plate · rod · wire |
| Producers | H.C. Starck · Plansee · Climax Molybdenum |
Learn more
Values are typical and for comparison only. For design, rely on the standard, the producer specification and the mill certificate. Sources: ASTM standards (B86, B386, B392/B393, B551, B708, B760 and others), producer data, and the METAL HUB materials database.
Updated: October 31, 2026