In the first set experiments, approximately 100 grams of ferrotungsten was placed into a heated laboratory tube furnace. The oxygen content of the oxidizing gas flowing through the furnace was maintained at 20% by volume (balance nitrogen) while effects of different gas flow rates and furnace temperatures were evaluated. After two hours, the boat was removed and allowed to cool. Once, the weight of the partially oxidized ferrotungsten was recorded, the partially oxidized ferrotungsten was placed in a second tube furnace and completely oxidized (900° C., air (21% O2) , 6 scfh). The final weight of the completely oxidized material was used to calculate the percent oxidation of the partially oxidized material at 2 hours. In the second set of experiments, the experimental setup was the same as the first except that the oxygen content was varied and the flow rate was fixed at 6 scfh.
FIG. 3 shows that the increase in the flow rate of gas through the furnace had a larger effect on the amount of oxidation after 2 hours than the increase in the furnace temperature. The highest percentage of oxidation after 2 hours was achieved using the combination of high temperature and high flow rate, i.e., 900° C. and 10 scfh. FIG. 4 shows that the increase in the oxygen content of the gas flowing through the furnace yielded a substantially greater percentage of oxidation after 2 hours than did the increase in furnace temperature. Again, the greatest amount of oxidation after 2 hours was obtained using the combination of higher O2 content and higher furnace temperature, i.e., 30% O2 and 900° C. Thus, the results of both experiments indicate that increasing the oxygen content of the furnace atmosphere either by increasing the flow rate of the oxygen containing gas or by increasing the oxygen content of the gas itself can significantly improve the oxidation rate.
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