MoSi 2 Oxidation in 670–1498 K Water Vapor

Molybdenum disilicide (MoSi 2 ) has well documented oxidation resistance at high temperature (T > 1273 K) in dry O 2 containing atmospheres due to the formation of a passive SiO 2 surface layer. However, its behavior under atmospheres where water vapor is the dominant species has received far less attention. Oxidation testing of MoSi 2 was performed at temperatures ranging from 670–1498 K in both 75% water vapor and synthetic air (Ar‐O 2 , 80%–20%) containing atmospheres. Here the thermogravimetric and microscopy data describing these phenomena are presented. Over the temperature range investigated, MoSi 2 displays more mass gain in water vapor than in air. The oxidation kinetics observed in water vapor differ from that of the air samples. Two volatile oxides, MoO 2 (OH) 2 and Si(OH) 4 , are thought to be the species responsible for the varied kinetics, at 670–877 K and at 1498 K, respectively. Increased oxidation (140–300 mg/cm 2 ) was observed from 980–1084 K in water vapor, where passivation is observed in air.