Comparison of Tungsten (Tungsten Heater) and Molybdenum for Heater Material

Common metals that have the lowest melting point include tin (232 ℃), lead (327 ℃), magnesium (651 ℃), zinc (419 ℃), antimony (630 ℃), aluminum (660 ℃), copper (1083 ℃), etc. However, under the low temperature (below 0℃) tin will destruct itself, and lead is soft with the low intensity, no metallic magnesium and zinc has active chemical property, which are easy to react with the non-metallic. Antimony is brittle and easy to volatilize when heated. In short, those materials are not suitable for coating of aluminum. Aluminum and copper have the metallic luster with high stability and low cost, so aluminum and copper are the most ideal coating materials. Tungsten and molybdenum are easy to oxidized at high temperatures, which is the key issue for them as a promising high-temperature structural materials.

Under a temperature below 300℃, molybdenum is relatively stable. A blue oxide film would formed over the surface if the temperature is higher than 300℃. The oxide film will evaporate if the temperature is higher than 500℃, It can be concluded that the higher the temperature, the faster the evaporation. White smoke MoO3 would be formed when over 700℃.

Wolfram of tungsten heater begins to oxidize in air at 400 ~ 500℃. If the temperature is above 600℃, WO₃ thin film would be formed on the surface, because the specific volume of WO₃ is greater than the base, tungsten wire would crack after reaching this temperature, increase the speed of oxidation. If the temperature is over 900℃, WO₃ would volatilize, then metal would be oxidized at a faster rate.

Therefore, the choice of tungsten or molybdenum as a heater material should be determined in according to the plated material, and to appropriately control the temperature.

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