Oxidation of Tungsten Metal by Air or Oxygen

Tungsten s sensitivity toward oxygen restricts its high-temperature application to protecting atmospheres or vacuum only. [Pg.85]

Adsorption. Oxygen is adsorbed on clean tungsten surfaces in a variety of atomic and molecular states. At low temperature ( 0 °C), oxygen is adsorbed molecularly, but at room temperature this adsorption is a precursor state to the atomic adsorption. A covered surface shows an ordered oxygen superstructure. If the temperature is increased, a more extensive coverage occurs and oxide-like structures are formed. The surface layer can be described as adsorbed oxide. [Pg.85]

The adsorption of oxygen on tungsten surfaces has been investigated most extensively. Relevant data can be found elsewhere [3.1]. [Pg.85]

Diffusion. Oxygen diffuses from the surface into the crystal lattice forming a bcc (a) solid solution. The solubility is very low. Calculated diffusion coefficients at 1700 °C are given as [Pg.85]

Permeation. For the diffusion of oxygen through tungsten in the temperature range 1950-2300 °C, the following relationship was found [Pg.85]

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