Contents
Refractory metals and their alloys differ widely in density, temperature behaviour and conductivity. This overview compares the five most frequently requested materials and shows what each is suited for.
What sets refractory metals apart
Refractory metals (high-melting-point metals) melt well above 2,000 °C and keep their strength at high temperatures. They include tungsten and molybdenum along with their alloys and composites. They are used where ordinary metals fail long before: in furnaces, in radiation shielding and in semiconductor and lighting technology. They are processed under shielding gas or vacuum, as they oxidise in air when hot.
The materials compared directly
The figures are guide values at room temperature and depend on grade, purity and manufacturing process. Composites (tungsten heavy alloy, copper-tungsten) have no single melting point – here the matrix limits the service temperature.
| Material | Density (g/cm³) | Melting point (°C) | Thermal cond. (W/m·K) | Typical application |
|---|---|---|---|---|
| Tungsten (W) | ≈ 19.25 | ≈ 3,422 | ≈ 170 | Electrodes, radiation sources, high temperature |
| Molybdenum (Mo) | ≈ 10.2 | ≈ 2,623 | ≈ 138 | Furnace building, heat shields, electrodes |
| TZM (Mo alloy) | ≈ 10.2 | ≈ 2,600 | ≈ 125 | Hot-working tools, loaded furnace parts |
| Tungsten heavy alloy (WNiFe) | 17.0–18.5 | ≈ 1,450 (matrix) | ≈ 70–90 | Balance weights, shielding, damping |
| Copper-tungsten (WCu) | ≈ 15–17 | ≈ 1,083 (Cu matrix) | ≈ 180–200 | Heat sinks, contacts, EDM electrodes |
How to choose the right material
- Highest temperature → tungsten or molybdenum/TZM.
- High density / a lot of mass in a small space → tungsten heavy alloy.
- Dissipate heat and match expansion to semiconductors → copper-tungsten.
- Mechanical load at high temperature → TZM instead of pure molybdenum.
- Good balance of temperature resistance, weight and machinability → molybdenum.
Frequently asked questions
Which is the densest metal in the comparison?
Pure tungsten at around 19.25 g/cm³. Tungsten heavy alloy (WNiFe) reaches 17.0 to 18.5 g/cm³ depending on tungsten content, while remaining machinable.
Which material has the highest melting point?
Tungsten at around 3,422 °C – the highest melting point of all metals. Molybdenum and TZM are around 2,600 °C. Composites such as copper-tungsten are limited by their matrix (copper ≈ 1,083 °C).
When do I use TZM instead of pure molybdenum?
TZM keeps its strength up to around 1,400 °C, while pure molybdenum recrystallises from about 1,100 °C. Under mechanical load at high temperature, TZM is the more stable choice.
Which material is suitable for heat sinks?
Copper-tungsten (WCu): it conducts heat almost as well as copper but can be matched in thermal expansion to semiconductors and ceramics, avoiding thermal stress at the joints.