Oxidation of Molybdenum 550° to 1700°C

Abstract

Weight change and oxygen consumption measurements were used to study the oxidation of molybdenum from 550 ~ to 1704~ for pressures of 5 to 76 Torr. For temperatures of 550~176 two processes occurred simultaneously, oxide scale formation and molybdenum trioxide volatility. Above 800~ at pressures up to 76 Tort molybdenum trioxide volatilized as fast as it formed. At 900~ and 76 Torr using 1.2 cm 2 samples the primary chemical reaction gave a rate of about 10 is at. molybdenum/cm2/sec. Above this temperature for 1.2 cm 2 specimens the reaction was limited by gaseous diffusion of oxygen. Little change was found in the rate of oxidation to 1615~ Pressure had only a small effect on the rate of reaction for these reaction conditions. However, in the chemically controlled region pressure had an important effect on the rate of oxidation. To extend the temperature region where the primary chemical reaction was rate controlling, samples of small area were used. A sample having a total area of 0.12 cm 2 gave a reaction rate of 8 x 10 is at./cm2/sec at 1410~ For these very fast reactions, appreciable temperature rises occurred, and the actual sample temperature had to be estimated. A log K vs. 1/T plot of the primary chemical

Oxidation and volatilization of TZM alloy in air

“…The high rate of volatilization is apparently linked to the increase in oxidation rate for these two temperatures as shown in Figure 1. Our data agree with that of Gulbransen, et al [1], where all of the oxygen reacted at 800°C in 76 torr oxygen and formed volatile oxides. The specimen tested at 800°C showed evidence of a molten layer.…”

“…Many of these studies have been oriented toward extremely high temperatures, e.g., up to 1700ºC, often under vacuum or environments with low oxygen activities [1,2,3,4].…”

“…Studies [1,5,6] on molybdenum at lower temperatures in high levels of oxygen report: 1) parabolic rate law at 250 to 450ºC, 2) linear behavior above 400ºC, 3) a role of MoO 2 and other oxides (MoO Z ), where 2 < Z < 3, between 450 to 650ºC, and 4) high vaporization of MoO 3 , mass loss and oxidation rates above 650ºC. We performed this study to explore conditions more typical to future fusion devices and to demonstrate predictive capabilities of a vaporization mass transport model.…”

Material Selection for Accident Tolerant Fuel Cladding

“…[10] These results were quite surprising and appeared to contradict decades old understanding of Mo oxidation. [24][25][26] In order to confirm…”

“…The competition between volatilization and oxide formation was noted earlier for this temperature range. [24] The effect of velocity on steam oxidation requires further study.…”