Oxidation of Mo-Re at reduced oxygen pressures

Rhenium generally improves the properties of molybdenum, and, therefore, there is interest in use of Mo-Re alloys in space system applications. Both Mo and Re have relatively low solubilities for oxygen but readily form oxide scales when exposed to oxidizing environments above ∼625 K. Studies are being conducted on Mo-41 Re to determine the rate of oxidation, type of scale formation, and effects on mechanical properties as a function of temperature and partial pressure of oxygen. Thus far, weight gains associated with formation of MoO2 have been found for PO2<10−3 Pa(10−5 torr) in vacuum, and weight losses associated with evaporation of MoO3 at 10−2 Pa. However, no significant changes in tensile properties were measured.