Lanthanated Tungsten Electrode Metal Injection Molding

The Metal Injection Molding (MIM) of insoluble metal is mainly used for manufacturing parts with complex and small size. The metal which produced by MIM isn’t has particularly high temperature strength and fatigue performance, but it can save a high of insoluble metal machining costs to achieve a nearly net shape. Traditional tungsten electrodes were produced by sintered tungsten bar and after machining to obtain pure or rare earth tungsten electrodes. Tungsten has highest melting point in insoluble metal, so machining is difficult and the cost is high, so using MIM to produce tungsten electrodes used in lighting equipment are more and more attention and favor in manufacturers. Compared with traditional method, tungsten electrode manufactured by MIM not only has complex shape which can use in different lighting equipment, but also has good performance. Pure tungsten and doped tungsten (AKS-W) is a common anode material, and thoriated tungsten, barium tungsten, and lanthanated tungsten electrode is often used as a cathode material.

Lanthanum tungsten electrodes (W-La₂O₃) manufactures by MIM, and the production processes are as following:
1. The La (NO₃) ₃ • 6H₂O was dissolved in alcohol and then mixed with tungsten powder (0.1um), in which La₂O₃ addition is 1.5%.
2. Place the mixture into a mixing ball mill for 24h, and then to employ drying and screening process. The milling medium is alcohol, grinding body is tungsten rod.
3. The sieved powder is baking and reduction at 600 ℃, so that La (NO₃) ₃ will decompose into La₂O₃.
4. Using paraffin-polymer binder to produce MIM feed. Determine the critical powder load in feed by torque rheometer. Since 1um tungsten powder produced feed has good flow, so the loading is used 55% of the volume fraction. Besides, the compounding temperature is 158 ℃, and roller speed is 60r / min.
5. Then after injection, degreasing and sintered will obtain lanthanated tungsten electrode.

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