Tungsten nano as well as micron sized particles were synthesized using thermal plasma method and now we want have BET analysis of that samples?
As the main goal of degassing is to remove any adsorbed species that could interfere with the physisorption measurements, the simple answer would be: any temperature that is able to remove all adsorbed species that is still low enough to not change your sample in any way.
For tungsten (assuming it has been exposed to air and is covered with some kind of oxide), the most important and difficult species to get rid of is most likely water. According to these proceedings water can be desorbed even below room temperature in a vacuum, which means that heating above the regular boiling point of water would usually do. (http://www.sciencedirect.com/science/article/pii/S0042207X96002837?np=y)
But as pure tungsten is a very high temperature material and should not sinter or change shape significantly below 800 or 900 degrees Celcius, I would recommend to use temperatures similar to those used for silica (300 degrees Celcius in a vacuum) to be certain everything is desorbed.
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