Tungsten is planned to be the main material for the first wall armor of future fusion reactors. Therefore, the investigation of tungsten oxidation addresses one safety aspect in an accident case, in which the cooling system fails and the temperature rises to about 1300 K at the wall of the fusion reactor vessel for several days. In such a situation, the ingress of air into the reactor vessel would lead to the formation of tungsten oxides, i.e. WO3 . WO3 as well as activated WO3 evaporate into the gas phase which should be avoided.The grain orientations have an influence of the oxidation and arestudied in this thesis in more detail. The grain orientations oftungsten (W) were analyzed using electron backscatter diffraction (EBSD)and were followed by oxidations in a range between 720 K and 870 K. Thegrain dependent oxidation rates were determined by measuring thethickness of the oxide layer. The data of the thickness measurement weretransformed into oxidation rates in mg^2/(cm^4 sec.) to compare themwith results obtained by gravimetric measurements.Tungsten grains with {100} orientation have the highest oxidation ratein a range of 720 K to 870 K, which is a factor of two higher than theoxidation rate of W grains with {111} orientation. The {110} orientationexhibits an oxidation rate in between the {100} and {111} orientation.
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