Tungsten melting electrode

Overview
The core components of discharge lamps include a cathode, an anode and supporting bars. Depending on lamp type, electrodes are delivered as complex moulded bodies or as simple pins. When voltage is applied between anode and cathode a bright arc forms; electrode tips must withstand temperatures of approximately 1,800–3,400 °C and transfer waste heat to the electrode body and support structure.

Your advantages at a glance

• High temperature stability up to 3,400 °C
• Excellent creep resistance
• Reduced electron work function thanks to oxide doping
• High thermal conductivity due to high core densities
• Good machinability for complex geometries
• High breaking strength for transport and assembly

Materials & types
Tungsten is the reference material for high-temperature electrodes: highest melting point, low vapour pressure, low thermal expansion and good thermal conductivity. Manufacturing processes and alloying/doping tailor dimensional stability, electron emission and mechanical machinability to specific lamp requirements.

Cathodes
Cathode materials include oxide-doped tungsten (e.g., AKS = aluminium-potassium silicate, La2O3) and WLZ (lanthanum + zirconium oxide doped tungsten). Oxide-doped grades are the non-radioactive alternative to thorium-doped materials. Porous tungsten or tungsten‑rhenium cathode bodies are available as blanks for infiltration (e.g., with barium oxide).

Anodes
Anodes must withstand the highest thermal loads. Potassium-doped tungsten grades are specified for anodes, providing superior high-temperature stability, creep resistance and burn-off behaviour. Special coatings can increase emissivity for extreme-load applications. Key examples:

• WVM = 30–70 µg/g potassium doping, Dm 2–13 mm
• WVMW = 15–40 µg/g potassium doping, Dm ≥13 mm
• S-WVMW = 15–40 µg/g potassium doping, Dm ≥35 mm

Supporting bars
Supporting bars carry cathodes and anodes and must resist mechanical shocks during transport and handling while providing good electrical and thermal conductivity. Suitable alloys include WVM and WL‑S; both remain particularly break-proof after high-temperature treatment during lamp production.

Materials table
Material | Dimensional stability | Electron emission | Diameter [mm] | Delivery form | Typical applications
WLZ | high | high | 6.0–25.0 | Rods and electrodes ready for installation | Cathodes
WL10 | medium | high | 1.2–80.0 | Wire, rods, and electrodes ready for installation | Anodes and cathodes
W porous | low | high | Upon request | Blanks, ready for infiltration | Cathodes
WL-S | medium | high | 5.0–10.0 | Wire, rods, and electrodes ready for installation | Supporting bars
WVM | high | low | 1.2–12.99 | Wire, rods, and electrodes ready for installation | Anodes and supporting bars
WVMW | high | low | 15.0–30.0 | Rods and electrodes ready for installation | Anodes
S-WVMW | high | low | 25.0–40.0 | Rods and electrodes ready for installation | Anodes

Notes
Materials can be supplied as wire, rods, blanks or electrodes ready for installation; porous forms are available for infiltration processes. Oxide-doped tungsten variants (e.g., La2O3, La+Zr oxides, AKS) lower the work function and are non-radioactive alternatives to thorium-doped tungsten. Contact supplier for custom diameters, tolerances and coating options.