The kinetics of oxidation of tungsten by CO2 was studied in a stagnation-flow reactor at CO2 partial pressures from 20 to 337 torr. The study covered the temperature range 2200°—3200°K and included measurements of the effect of CO on the reaction kinetics at CO/CO2 ratios up to 5:1. The rates observed below about 2650°K were essentially independent of the velocity of the impinging gas stream, indicating that the surface kinetics primarily determined the rates up to 2650°K at the lower gas-flow rates used and to higher temperatures at higher flow rates. Where surface kinetics were rate determining, the data could be explained simply by incorporating a temperature-dependent ``sticking coefficient'' for CO2 into the two-layer adatom model previously proposed for the W–O2 reaction. The effect of CO was small and was readily incorporated into the model. Velocity-dependent deviations from the rates predicted by the model were observed at temperatures above 2650°K. These were largely explained by simple mass-transfer theory. At low flow rates and high temperatures it appears that the reactions of desorbed oxygen became important.

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An arc-image stagnation-flow reactor has been developed to study the rates of gas-solid reactions between 2000 and 3000°K. Most refractory solids can be heated in this reactor to their melting points in a partial atmosphere of almost any gas except strong oxidizers such as fluorine. The standard deviation of a datum point, in the case of oxidation of tungsten by CO2 at 100 Torr, is 6% at 2500°K, corresponding to a temperature uncertainty of ±9°K.

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