W-Revalues describe: W-25Re
Vacuum electronics & X-ray sources
Why it wins
Rhenium buys ductility and thermal-fatigue resistance in refractories: W-Re focal tracks resist crazing on rotating anodes, W-Re wires make C-type thermocouples to 2300 C.
Why not the alternative
Pure tungsten tracks craze early and the spectrum drifts; pure Mo joints crack.
Watch out
Cost: rhenium is one of the rarest stable elements.
Properties
The values below are candidate: compiled from the sources named, not yet individually validated.
Provisional provenance: Plansee refractory metal and alloy data.
Wet cleaning
| Recipe | degrease, DI rinse, hydrogen fire |
|---|
| Forbidden | oxidising conditions hot: Re₂O₇ is volatile and toxic |
|---|
| Limit | oxide volatility, not cleanliness |
|---|
Vacuum and outgassing
| Outgassing, unbaked (10 h) | 1e-9 mbar·L/s/cm² |
|---|
| Outgassing, baked | 1e-12 mbar·L/s/cm² |
|---|
| Vapour pressure | negligible below 2200 °C |
|---|
Temperature
| Bake, assembled | 450 °C |
|---|
| Vacuum degas | 1500 °C |
|---|
| Braze / H2 firing | 1800 °C |
|---|
| Metallurgical limit | no DBTT problem: that is the point of the rhenium |
|---|
Thermal
| CTE | 4.8 ppm/K |
|---|
| Thermal conductivity | 70–100 W/m·K |
|---|
| Specific heat | 150 J/kg·K |
|---|
| Emissivity | 0.1 |
|---|
| Melting / softening | 3000–3180 °C |
|---|
Mechanical
| Strength | 1000+ ys MPa |
|---|
| Tensile | 1200–1800 MPa |
|---|
| Elongation | 10–20 % |
|---|
| Young's modulus | 400–460 GPa |
|---|
| Hardness | 400–500 HV |
|---|
| Density | 19.7 (W-25Re) g/cm3 |
|---|
Electrical and magnetic
| Relative permeability | ~1.0 |
|---|
| Resistivity | 25–30 |
|---|
Engineering
| Corrosion | inert in vacuum |
|---|
| Joining | brazed; ductile enough to draw as wire |
|---|
| Process notes | the rhenium ductilising effect buys the workability |
|---|
| Availability and cost | rhenium is rare and priced accordingly |
|---|
Grades
| W-5Re / W-26Re | anode focal tracks and thermocouple pairs |
|---|
| Mo-47.5Re | ductile weldable refractory assemblies |
|---|
Sources · 1
- Plansee refractory alloy data
← The Matter